Saturday, July 20, 2013

Giant Breach in Earth's Magnetic Field Discovered - NASA Science

Giant Breach in Earth's Magnetic Field Discovered - NASA Science 

Giant Breach in Earth's Magnetic Field Discovered

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Dec. 16, 2008: NASA's five THEMIS spacecraft have discovered a breach in Earth's magnetic field ten times larger than anything previously thought to exist. Solar wind can flow in through the opening to "load up" the magnetosphere for powerful geomagnetic storms. But the breach itself is not the biggest surprise. Researchers are even more amazed at the strange and unexpected way it forms, overturning long-held ideas of space physics.
"At first I didn't believe it," says THEMIS project scientist David Sibeck of the Goddard Space Flight Center. "This finding fundamentally alters our understanding of the solar wind-magnetosphere interaction."
The magnetosphere is a bubble of magnetism that surrounds Earth and protects us from solar wind. Exploring the bubble is a key goal of the THEMIS mission, launched in February 2007. The big discovery came on June 3, 2007, when the five probes serendipitously flew through the breach just as it was opening. Onboard sensors recorded a torrent of solar wind particles streaming into the magnetosphere, signaling an event of unexpected size and importance.
Right: One of the THEMIS probes exploring the space around Earth, an artist's concept. [more]
"The opening was huge—four times wider than Earth itself," says Wenhui Li, a space physicist at the University of New Hampshire who has been analyzing the data. Li's colleague Jimmy Raeder, also of New Hampshire, says "1027 particles per second were flowing into the magnetosphere—that's a 1 followed by 27 zeros. This kind of influx is an order of magnitude greater than what we thought was possible."
The event began with little warning when a gentle gust of solar wind delivered a bundle of magnetic fields from the Sun to Earth. Like an octopus wrapping its tentacles around a big clam, solar magnetic fields draped themselves around the magnetosphere and cracked it open. The cracking was accomplished by means of a process called "magnetic reconnection." High above Earth's poles, solar and terrestrial magnetic fields linked up (reconnected) to form conduits for solar wind. Conduits over the Arctic and Antarctic quickly expanded; within minutes they overlapped over Earth's equator to create the biggest magnetic breach ever recorded by Earth-orbiting spacecraft.
Above: A computer model of solar wind flowing around Earth's magnetic field on June 3, 2007. Background colors represent solar wind density; red is high density, blue is low. Solid black lines trace the outer boundaries of Earth's magnetic field. Note the layer of relatively dense material beneath the tips of the white arrows; that is solar wind entering Earth's magnetic field through the breach. Credit: Jimmy Raeder/UNH. [larger image]
The size of the breach took researchers by surprise. "We've seen things like this before," says Raeder, "but never on such a large scale. The entire day-side of the magnetosphere was open to the solar wind."
The circumstances were even more surprising. Space physicists have long believed that holes in Earth's magnetosphere open only in response to solar magnetic fields that point south. The great breach of June 2007, however, opened in response to a solar magnetic field that pointed north.
"To the lay person, this may sound like a quibble, but to a space physicist, it is almost seismic," says Sibeck. "When I tell my colleagues, most react with skepticism, as if I'm trying to convince them that the sun rises in the west."
Here is why they can't believe their ears: The solar wind presses against Earth's magnetosphere almost directly above the equator where our planet's magnetic field points north. Suppose a bundle of solar magnetism comes along, and it points north, too. The two fields should reinforce one another, strengthening Earth's magnetic defenses and slamming the door shut on the solar wind. In the language of space physics, a north-pointing solar magnetic field is called a "northern IMF" and it is synonymous with shields up!
"So, you can imagine our surprise when a northern IMF came along and shields went down instead," says Sibeck. "This completely overturns our understanding of things."
Northern IMF events don't actually trigger geomagnetic storms, notes Raeder, but they do set the stage for storms by loading the magnetosphere with plasma. A loaded magnetosphere is primed for auroras, power outages, and other disturbances that can result when, say, a CME (coronal mass ejection) hits.
The years ahead could be especially lively. Raeder explains: "We're entering Solar Cycle 24. For reasons not fully understood, CMEs in even-numbered solar cycles (like 24) tend to hit Earth with a leading edge that is magnetized north. Such a CME should open a breach and load the magnetosphere with plasma just before the storm gets underway. It's the perfect sequence for a really big event."
Sibeck agrees. "This could result in stronger geomagnetic storms than we have seen in many years."
A video version of this story may be found here. For more information about the THEMIS mission, visit http://nasa.gov/themis
more information
What happened to conventional wisdom? Researchers at the University of New Hampshire are using computer models to unravel the basic physics of the great breach. They're finding that reconnection at the poles is key. Conventional wisdom held that equatorial reconnection was more important, which is why the giant breaches were not anticipated until THEMIS flew through one.
more stories about THEMIS:
THEMIS, short for Time History of Events and Macroscale Interactions during Substorms, is the fifth medium-class mission under NASA's Explorer Program. The program, managed by The Explorers Program Office at Goddard Space Flight Center, Greenbelt, Md., provides frequent flight opportunities for world-class space investigations in Heliophysics and Astrophysics. The University of California, Berkeley's Space Sciences Laboratory managed the project development and is currently operating the THEMIS mission. Swales Aerospace, Beltsville, Md., built the THEMIS satellites.
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    Amy | June 12th, 2013
    By Dr. Amy Keesee, WVU Plasma Physicist. On April 13, 2013, social media was abuzz with predictions that there would be good viewing conditions for aurora in the northern United States. Many people went outside that night to look up, but unfortunately, there wasn’t much to see. While many may have been disappointed, this was an excellent opportunity for the general public to learn about the Sun, geomagnetic storms, and space weather. In particular, while such activity from the Sun and the resulting geomagnetic storms can have (potentially negative) effects on humans and our technology (see previous posts by Paul and myself), it is important to note that our ability to predict such space weather is in its infancy.The Sun is monitored by numerous instruments on satellites such as the Solar Dynamics Observatory (SDO), the Solar and Heliospheric Observatory (SOHO), and the dual-satellite mission STEREO. These instruments observed a coronal mass ejection launched from the Sun on April 11th. These images can be seen using the NASA Integrated Space Weather Analysis System. Using calculations of the speed and direction of the coronal mass ejection (CME) from these images, scientists predict whether the CME will hit Earth, including whether it will be a direct or glancing blow, as well as an approximate time. Scientists also use models to predict these characteristics. One such model is the WSA-ENLIL-CONE model. The model of the Earth-directed CME that launched from the Sun on March 15, 2013 can be seenhere. In this image, the Sun is the white circle and Earth is the yellow circle. AccuWeather created a map of auroral viewing conditions for April 13th. aurora_viewing What may have caused confusion with this map is that it was not a prediction of the aurora itself, but an assessment of the cloud cover in the region of possible auroral viewing zones. However, the cutoff used to indicate the “not visible” region is based on a storm with a Kp index of 9. It would require a very intense geomagnetic storm to reach such levels. The Kp index is a scale, similar to the Richter scale for earthquakes, that is based on measurements of the changes in Earth’s magnetic field caused by currents driven in space by the storm. Stronger storms drive stronger currents, and thus larger changes in magnetic field measurements. Aurora are often seen at high latitudes, even during weak storms. As the storms grow stronger, the aurora can be seen at lower latitudes. It turned out that the CME that hit Earth on April 13th drove a relatively weak event, with a Kp index of 4. One reason for the weak storm was that the CMEcontained a primarily northward pointing magnetic field. One of the drivers of large storms is magnetic reconnection of the magnetic field in the CME with Earth’s magnetic field. (Learn more about reconnection in Luke’s post.) The magnetic fields must be pointing in opposite directions to occur. Earth’s magnetic field is like a bar magnet, with the magnetic field lines coming out of the South geographic pole and into the North geomagnetic pole, so that they point northward. For reconnection to occur, the magnetic field in the CMEmust, therefore, point southward. We currently do not have the ability to predict which direction the magnetic field in the CME is pointing. There are satellites with instruments that can measure the magnetic field in the CME, but their location gives about a one-hour notice prior to the CME hitting Earth’s magnetic field. Plasma physicists at WVU are working to understand many elements of the Sun-Earth system, including coronal mass ejections, magnetic reconnection, and the dynamics of geomagnetic storms. Hopefully in the future, scientists will be able to predict space weather with similar accuracy to the regular weather forecasts. Find out more about Plasma Physics at West Virginia University athttp://ulysses.phys.wvu.edu/~plasma.

    Predicting Aurora Sightings

     Magnetic Reconnection in the Magnetosphere

    Contents

     [hide]

    Chairs

    Paul Cassak, West Virginia University (Paul.Cassak [at] mail.wvu.edu)
    Andrei Runov, University of California Los Angeles (arunov [at] igpp.ucla.edu)
    Homa Karimabadi, University of California San Diego (homakar [at] gmail.com)

    2013 GEM Workshop Plans

    At the workshop, we are having four 1.5 hr-long sessions to discuss:
    • Dayside reconnection and its relation to transient phenomena at the magnetopause and bow shock (joint with Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures focus group)
    • Magnetotail reconnection and its role in substorms, pseudo breakups, PBIs and other substorm-related phenomena (joint with Substorm Expansion Onset focus group)
    • General problems of magnetospheric reconnection. Nominally, the session activities will address Signatures of Kinetic Scale Reconnection Physics (a prelude to the launch of MMS), but contributions on any topic including onset, evolution, and consequences are welcomed
    We welcome contributions based upon data analysis, simulations, and theory.

    2013 GEM Workshop Schedule and Expected Speakers

    1:30 pm - 3:00 pm on Tuesday (June 18), joint with Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures focus group
    Expected speakers (in alphabetical order)
    1. Yaireska Colladovega, determining motion of FTEs on the dayside magnetopause
    2. Shiva Kavosi, simulations of Kelvin-Helmholtz Instability observed by THEMIS
    3. Sunhee Lee, cold ion behavior during magnetic reconnection at the magnetopause
    4. Xuanye Ma, interaction of Kelvin-helmholtz and reconnection for large magnetic shear
    5. Takuma Nakamura, vortex induced reconnection
    6. Karlheinz Trattner, Tracing multiple X-lines at the magnetopause
    7. Rick Wilder, reconnection at high-latitude magnetopause with extreme density asymmetry
    8. Binzheng Zhang, soft electron precipitation bifurcations during large By driving
    10:30 am - 12:15 pm on Wednesday (June 19), joint with Substorm Expansion Onset focus group
    Expected speakers (in alphabetical order)
    1. Joachim Birn (w/M. Hesse), near tail reconnection: onset
    2. Joachim Birn (w/M. Hesse), near tail reconnection: energy conversion
    3. Jim Drake, structure of reconnection exhausts and dipolarization fronts
    4. Stefan Kiehas, reconnection observations with THEMIS/ARTEMIS
    5. Andrei Runov, Update on Cluster and THEMIS/ARTEMIS observations
    6. Mikhail Sitnov, magnetotail reconnection onset and dipolarization fronts
    7. Mikhail Sitnov (w/S. Merkin), magnetotail reconnection onset: kinetic vs. MHD
    1:30 pm - 3:00 pm and 3:30 - 5:00pm on Wednesday (June 19)
    Expected speakers (in alphabetical order)
    1. Amitava Bhattacharjee, plasmoids
    2. Joachim Birn, energetic particle fluxes & anisotropies at dipolarization fronts
    3. Joe Borovsky, solar wind coupling
    4. Paul Cassak, shear flow
    5. Lars Daldorff, PIC/BATS-R-US coupling
    6. John Dorelli, global Hall-MHD effects on magnetospheric convection
    7. John Dorelli, sw/ms coupling
    8. Jan Egedal, role of pressure anisotropy
    9. Stefan Eriksson, solar wind reconnection
    10. Gabor Facsko, solar wind disturbances forcing magnetotail reconnection
    11. Michael Hesse, asymmetric reconnection
    12. Colin Komar, dayside separators
    13. Yanhua Liu, counter streaming heavy ions in reconnection
    14. Kittipat Malakit, asymmetric reconnection
    15. Tai Phan, electron heating
    16. Mike Shay, electron heating
    17. Brian Walsh, plasmaspheric drainage plumes

    Archive - Focus Group Proposal (2012)

    Abstract

    Magnetic reconnection underlies the dynamics in many aspects of magnetospheric physics and is critical to the development of a predictive understanding of space weather phenomena. It importance spans from the dayside where solar wind-magnetospheric coupling occurs to the nightside where storm and substorm phenomena occur. Many existing Focus Groups treat reconnection in the context of a particular application, but a Focus Group specifically on reconnection is being proposed to develop an understanding that could not be attained from studies on particular applications. Broadly, the proposed Focus Group will address kinetic physics of reconnection and how it couples to macroscales, reconnection at the dayside and its relation to solar wind-magnetospheric coupling, three-dimensional reconnection, reconnection onset and transient behavior and implications for transport, and particle acceleration in reconnection. The proposed Focus Group is timely as simulations have matured to the point where they can offer realistic comparisons to observations, and the existing THEMIS/ARTEMIS and upcoming MMS missions include reconnection physics as a key feature of their goals. Reconnection is by nature cross-disciplinary and offers many opportunities for interaction with existing Focus Groups. The proposed reconnection Focus Group is for five years, and will produce deliverables of import for many aspects of GEM goals.

    Topic Description

    During magnetic reconnection, a change in magnetic topology facilitates the conversion of magnetic energy to kinetic and thermal energy and allows mixing of plasmas on either side of current sheets. It is the driver of many dynamical behaviors in the magnetosphere that are of crucial importance to space weather. At the dayside magnetopause, reconnection plays a critical role in solar wind-magnetospheric coupling and recent evidence suggests it may even control the coupling efficiency. This process is the driver of magnetospheric convection, evolution of the radiation belts, and loading of energy in the magnetotail. The release of this energy in geomagnetic storms and substorms is a result of reconnection in the magnetotail. Reconnection also produces energetic particles that can damage satellites. At present, magnetic reconnection is studied separately under the auspices of particular applications within separate GEM Focus Groups. The proposed Focus Group will address the physics of reconnection as a distinct physical process which is important for magnetospheric applications in ways that cannot be addressed in applied settings. There is a long history of success in GEM on reconnection (including the highly-cited GEM Reconnection Challenge). The proposed Focus Group will foster interaction between observations, simulations, and models. The broad goals of the Reconnection Focus Group are to contribute to the understanding of (1) the kinetic microphysics of reconnection and how it couples to the magnetosphere at macroscales, (2) how and where dayside reconnection occurs and how it contributes to solar wind-magnetospheric coupling including the role of flux transfer events, (3) how three-dimensional reconnection proceeds, especially at the dayside, (4) the onset of reconnection and the physics of transient reconnection events and their relation to bursty bulk flows, dipolarization fronts, and entropy bubbles, and (5) how reconnection produces energetic particles. Recent advances in fluid and kinetic simulations both locally at reconnection sites and globally containing the whole magnetosphere have led to a point where realistic numerical models can be compared directly with satellite observations. The Focus Group will benefit from a wealth of observational data from existing satellites, as well as new highly resolved multi-point observational data from the THEMIS/ARTEMIS mission and the upcoming Magnetospheric MultiScale (MMS) mission. Strong ties with existing Focus Groups studying applications of reconnection will be made.

    Timeliness of the Focus Group

    A GEM Focus Group on magnetic reconnection is particularly timely. NASAs Magnetospheric MultiScale (MMS) Mission, with a planned launch date of October of 2014, "will use Earth's magnetosphere as a laboratory to study magnetic reconnection" (http:// mms.gsfc.nasa.gov/about_mms.html), focussing on the kinetic-scale microphysics. This requires spacecraft to be closer together than previous missions and will provide unprecedented observational resolution. The three-probe THEMIS constellation will also be reconfigured to form a larger scale tetrahedron with MMS at one node to provide the macroscopic context for the microscopic measurements by MMS. In addition, the ARTEMIS satellites repurposed from the THEMIS mission have recently moved into a lunar orbit and will provide information on the mid-tail region where reconnection is expected to occur and serve as a solar wind monitor on the dayside. Therefore, near-future in-situ observations will provide measurements at a wide scale range from the electron kinetic scale to the global scale. In the run-up to launch of MMS, a GEM Focus Group on reconnection emphasizing numerical and observational studies will play a central role in preparing for the mission by investigating what signals should be expected and in what locations of the magnetosphere. After the launch of MMS, the GEM Focus Group will be an avenue for analyzing and interpreting the data with comparisons to simulations and for putting the newly obtained knowledge in context of larger-scale magnetospheric behavior.

    Relation to Existing GEM Focus Groups

    As magnetic reconnection underlies dynamics in every GEM Research Area, this Focus Group has enormous potential for interaction with existing Focus Groups. It is the goal of this Focus Group to both support existing efforts in other Focus Groups and to drive new avenues of research through discovery achieved in this Focus Group. A non-exhaustive discussion follows for ways in which a reconnection Focus Group is synergistic with existing Focus Groups. For each example listed, the Co-Chairs of the existing Focus Group have been contacted and agree that interdisciplinary activities with a reconnection Focus Group would be desirable.
    1. Plasmasphere-Magnetosphere Interactions (2008-13) - The PMI Focus Group is an example where previous incarnations of reconnection studies at GEM have successfully had interdisciplinary activities. The previous reconnection focus group produced studies on asymmetric reconnection and how it may occur at the dayside magnetosphere. Recent studies showed that solar wind-magnetospheric coupling is less efficient when high density plasmaspheric drainage plumes reach the dayside reconnection site. This is consistent with reconnection becoming less efficient when asymmetric reconnection occurs with high density plasma. A presentation on this was given in a PMI session. Though the PMI Focus Group will end soon, it is expected that the previous interdisciplinary activities will continue.
    2. Substorm Expansion Onset: The First 10 Minutes (2008-13) - This is another example where there has been cross-participation in the past. The physics of dipolarization fronts and how they can be used to understand reconnection onset in substorms is common to both groups, as it was recently determined that they occur at the onset of reconnection. Kinetic simulations have been very useful to understand their properties.
    3. Magnetosheath (2010-14) - The magnetosheath is strongly linked to dayside reconnection physics. Many issues of the structure of the magnetosheath are related to how reconnection proceeds, such as the appearance or lack of flux pile-up at the magnetopause and the propensity for flux transfer events. Understanding how kinetic effects impact dayside reconnection and the march to global kinetic modeling, and where reconnection at the dayside occurs as a function of solar wind conditions, are both synergistic topics.
    4. Metrics and Validation (2011-15) - This group addresses challenges of model-data comparisons and how to assess them. In the past, a barrier to performing careful metrics and validation studies of magnetic reconnection has been a lack of sufficient observations, but the MMS mission is expected to change this. Therefore, a potential avenue for collaboration with the Metrics and Validation Focus Group is comparisons of kinetic modeling and observational data from MMS.
    5. Tail-Inner Magnetosphere Interactions (2012-16) - This Focus Group addresses modes of transport that cause heating in the magnetotail and inner magnetosphere. It is thought that transient events such as bursty bulk flows, entropy bubbles, and dipolarization fronts play a potentially important role. As these events are associated with magnetotail reconnection, there is strong potential for cross-disciplinary interactions with this Focus Group.

    Goals and Deliverables

    The goals of the Reconnection Focus Group are to understand aspects of magnetospheric reconnection with an eye to applications in other Focus Groups. This list is not exhaustive, but it has been compiled using input from the GEM community.
    1. What is the physics of reconnection at the kinetic scale and how does it couple to the magnetosphere at macro-scales? Particular topics include the role of the extended electron diffusion region, pressure anisotropies, normal magnetic fields for magnetotail applications, asymmetries in density and magnetic field, and whether or how the microphysics of reconnection can be incorporated into fluid models in geospace general circulation models (GGCMs). Examples of deliverables for simulation and modeling work include answers to the following questions - What sets the scale of the extended electron diffusion region and what is its effect on reconnection? (This will be important both before and after the launch of MMS for locating and analyzing reconnection events.) How do asymmetries effect the kinetic signatures of reconnection? Under what conditions do pressure anisotropies arise? Observational deliverables include THEMIS/ARTEMIS and MMS results, which will be compared to numerical simulations.
    2. How does reconnection proceed at the dayside and how does it contribute to solar wind-magnetospheric coupling? Topics include the role of asymmetries and shear flow in setting the efficiency of reconnection and the role of flux transfer events. Deliverables include quantitative predictions of dayside reconnection efficiency as a function of solar wind conditions that can be fed into solar wind-magnetospheric coupling functions as in the Borovsky coupling function and expected properties of flux transfer events in kinetic simulations and observations.
    3. How does three-dimensional reconnection proceed, especially at the dayside? Numerical deliverables include answering these questions - What is the location of reconnection on the dayside and its efficiency as a function of solar wind conditions? What differences are there between in 2D and fully 3D reconnection? Observational deliverables include signatures of the dissipation region in fully 3D settings and their meso- and macro-scale ramifications.
    4. How does reconnection onset and what is the physics of transient reconnection events such as bursty bulk flows, dipolarization fronts, entropy bubbles, and flux transfer events? Deliverables include how their properties depend on magnetospheric conditions, their role in energy and mass transport, how they expand and spread as a function of time, and comparisons with observational data from the THEMIS/ARTEMIS mission.
    5. How are energetic particles produced during reconnection? This includes mechanisms based on reconnection electric fields and secondary islands. Deliverables include the relative importance of various particle acceleration mechanisms and the observational signatures that result, and observations of these events from THEMIS/ARTEMIS and MMS.

    Co-Chairs

    • Paul Cassak, West Virginia University, Paul.Cassak [at] mail.wvu.edu (Expertise - Local and global fluid simulations, local kinetic simulations)
    • Andrei Runov, University of California, Los Angeles, arunov [at] igpp.ucla.edu (Expertise - Magnetotail observations)
    • Homa Karimabadi, University of California, San Diego, homakar [at] gmail.com (Expertise - Local and global kinetic simulations)

    Term of Focus Group

    Five years (2013-2017)

    Expected Activities, Session Topics, and Challenges

    The following are a possible set of activities and session topics for the duration of the proposed Focus Group. This list is not intended to be binding, nor is it intended to be noninclusive to research in areas planned for other years, but is offered as a guide to the direction of the Focus Group. Year 1, Signatures of Kinetic Scale Reconnection Physics (2013) - This is important in the runup to the launch of the MMS mission. The state-of-the-art in kinetic simulations will be gathered and discussed in relation to existing observational data to make predictions for MMS. Year 2, Dayside Reconnection and Solar Wind-Magnetospheric Coupling (2014) - This activity will collect progress in determining how reconnection occurs at the magnetopause and how it impacts solar wind-magnetospheric coupling. Cross-disciplinary activities with the Magnetosheath group are possible. Year 3, Kinetic Physics of Reconnection and Particle Acceleration (2015) - With early results from MMS expected, this session will focus on analyzing this data and comparing it to numerical simulations. It is expected that particle acceleration will be a strong component of the observations. Cross-disciplinary activities with the Metrics and Validation group are possible. Year 4, Reconnection Onset and Transients (2016) - This session will address the role of transients and reconnection onset. Cross-disciplinary activities with the Tail-Inner Magnetosphere Interactions group are possible. Year 5, Understanding Three-dimensional Reconnection (2017) - Efforts on the challenging and largely unknown physics of three-dimensional reconnection will be gathered and discussed.
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