Ramiz Qudsi
From state of caffeination to citation!
A comparative study of reconnection
X-line predictions on dayside magnetopause of Earth
Ramiz A. Qudsi, Brian Walsh, J. Broll
Boston University, Los Alamos National Lab
*(qudsira@bu.edu)
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Link to the presentation
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Outline:
- Magnetic Reconnection and x-line
- Location of x-line
- Different models
- Data
- Results
- Discussions
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The BASICS
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Source: NASA
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[Broll et al., 2017]
Source: wikipedia
Magnetic Reconnection
Why Magnetic Reconnection?
Gotta work on something!
Why not?
Ubiquitous nature of reconnection
Energy dynamics
Dynamo effect
Region of interest:
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Location of x-line
Local field bisection [Moore et al., 2002]
Maximum exhaust speed [Swisdak and Drake, 2007]
Maximum magnetic shear [Trattner et al., 2007]
Maximum reconnecting field energy [Hesse et al., 2013]
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Magnetic shear:
\cos(\theta) = \left(\textbf{B}_{\rm sh} \cdot \textbf{B}_{\rm msp}\right)/ \left(|\textbf{B}_{\rm sh}| |\textbf{B}_{\rm msp}|\right)
B_{\rm rec} = |\textbf{B}_{\rm msp} \cdot \textbf{i}_{\rm xn}|
Local field bisection:
Reconnection field energy:
E \propto \left(B_{\rm sh}^2 \times B_{\rm msp}^2\right)
Exhaust speed:
V_{\rm A} = \left[\frac{B_{\rm sh} B_{\rm msp} \left(B_{\rm sh} + B_{\rm msp}\right)}{\left(n_{\rm p,msp}B_{\rm sh} + n_{\rm p,sh}B_{\rm msp}\right)} \right]^{1/2}
sh: magnetosheath
msp: magnetosphere
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DATA
Data:
Solar
Wind
T-96 and IGRF Model
OMNI
Cooling-2001 Model
Magnetosheath
Magnetopause
Shue-1998 Model
Data
Solar Wind data: OMNI (propagated to the magnetopause)
Observational data: MMS (FPI and FGM)
Magnetospheric magnetic field: Models (T96 or T05 and IGRF)
Magnetosheath magnetic field: Models (Cooling model)
x
z
y
GSM coordinate system
Magnetopause stand-off point: Models (Shue Model)
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Magnetosheath
Magnetosphere
[Broll et al., 2017]
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RESULTS
The maximum shear model
The maximum exhaust velocity model
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DISCUSSIONS
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Discussions:
Most model fail when the z-component of magnetic field is positive. Though reconnection energy model seem to perform better than other 3.
The spread in the histogram of shear model appear to be maximum.
Need a lot more reconnection events for a better understanding.
As expected, different models predict different location of x-lines for the same dataset.
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Thank You!
Link to the presentation
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Thank You!
Link to the presentation
Qudsi BU qudsira@bu.edu
If Paul asks his question:
- Both earth and the sun are kind of like magnets and thus have magnetic fields around them.
- These collide in space and a lot of energy is released.
- Several model predict where that process happens.
- We are trying to find out which is the most accurate model most of the time and which one is most accurate only sometimes (under specific conditions).
Reconnection
By Ramiz Qudsi
Reconnection
A comparative study of reconnection X-line predictions on dayside magnetopause of Earth. Magnetic reconnection is a fundamental plasma process of key importance to several fields. Reconnection at Earth’s magnetopause drives magnetospheric convection and provides mass and energy input into the magnetosphere/ionosphere system. Despite this importance, the factors governing the location of dayside magnetopause reconnection are not well understood. Though a few models can predict X-line locations reasonably well the underlying physics is still unresolved. In this study we present results from an intensive analysis of over 100 reconnection regions observed by MMS to determine what quantities are most strongly associated with the occurrence of dayside magnetopause reconnection. We also attempt to answer under what upstream conditions are global X-line models least reliable.
