scholarly journals Solar wind conditions leading to efficient radiation belt electron acceleration: A superposed epoch analysis

2015 ◽  
Vol 42 (17) ◽  
pp. 6906-6915 ◽  
Author(s):  
W. Li ◽  
R. M. Thorne ◽  
J. Bortnik ◽  
D. N. Baker ◽  
G. D. Reeves ◽  
...  
Keyword(s):  
Solar Wind ◽  
Radiation Belt ◽  
Electron Acceleration ◽  
Superposed Epoch Analysis ◽  
Epoch Analysis

scholarly journals Different magnetospheric modes: solar wind driving and coupling efficiency

2009 ◽  
Vol 27 (11) ◽  
pp. 4281-4291 ◽  
Author(s):  
N. Partamies ◽  
T. I. Pulkkinen ◽  
R. L. McPherron ◽  
K. McWilliams ◽  
C. R. Bryant ◽  
...  
Keyword(s):  
Solar Wind ◽  
Solar Wind Speed ◽  
Coupling Efficiency ◽  
Slow Solar Wind ◽  
Cycle Phase ◽  
Particle Injection ◽  
Superposed Epoch Analysis ◽  
Magnetospheric Convection ◽  
Epoch Analysis ◽  
Steady Convection

Abstract. This study describes a systematic statistical comparison of isolated non-storm substorms, steady magnetospheric convection (SMC) intervals and sawtooth events. The number of events is approximately the same in each group and the data are taken from about the same years to avoid biasing by different solar cycle phase. The very same superposed epoch analysis is performed for each event group to show the characteristics of ground-based indices (AL, PCN, PC potential), particle injection at the geostationary orbit and the solar wind and IMF parameters. We show that the monthly occurrence of sawtooth events and isolated non-stormtime substorms closely follows maxima of the geomagnetic activity at (or close to) the equinoxes. The most strongly solar wind driven event type, sawtooth events, is the least efficient in coupling the solar wind energy to the auroral ionosphere, while SMC periods are associated with the highest coupling ratio (AL/EY). Furthermore, solar wind speed seems to play a key role in determining the type of activity in the magnetosphere. Slow solar wind is capable of maintaining steady convection. During fast solar wind streams the magnetosphere responds with loading–unloading cycles, represented by substorms during moderately active conditions and sawtooth events (or other storm-time activations) during geomagnetically active conditions.

scholarly journals Dynamics of large‐scale solar wind streams obtained by the double superposed epoch analysis

2015 ◽  
Vol 120 (9) ◽  
pp. 7094-7106 ◽  
Author(s):  
Yu. I. Yermolaev ◽  
I. G. Lodkina ◽  
N. S. Nikolaeva ◽  
M. Yu. Yermolaev
Keyword(s):  
Solar Wind ◽  
Large Scale ◽  
Superposed Epoch Analysis ◽  
Epoch Analysis

scholarly journals Superposed epoch analysis applied to large-amplitude travelling convection vortices

1998 ◽  
Vol 16 (7) ◽  
pp. 743-753 ◽  
Author(s):  
H. Lühr ◽  
M. Rother ◽  
T. Iyemori ◽  
T. L. Hansen ◽  
R. P. Lepping
Keyword(s):  
Solar Wind ◽  
Large Amplitude ◽  
Selection Criteria ◽  
Solar Rotation ◽  
Current System ◽  
Azimuthal Direction ◽  
Superposed Epoch Analysis ◽  
Northern Half ◽  
Epoch Analysis ◽  
Image Network

Abstract. For the six months from 1 October 1993 to 1 April 1994 the recordings of the IMAGE magnetometer network have been surveyed in a search for large-amplitude travelling convection vortices (TCVs). The restriction to large amplitudes (>100 nT) was chosen to ensure a proper detection of evens also during times of high activity. Readings of all stations of the northern half of the IMAGE network were employed to check the consistency of the ground signature with the notation of a dual-vortex structure moving in an azimuthal direction. Applying these stringent selection criteria we detected a total of 19 clear TCV events. The statistical properties of our selection resemble the expected characteristics of large-amplitude TCVs. New and unexpected results emerged from the superposed epoch analysis. TCVs tend to form during quiet intervals embedded in moderately active periods. The occurrence of events is not randomly distributed but rather shows a clustering around a few days. These clusters recur once or twice every 27 days. Within a storm cycle they show up five to seven days after the commencement. With regard to solar wind conditions, we see the events occurring in the middle of the IMF sector structure. Large-amplitude TCVs seem to require certain conditions to make solar wind transients 'geoeffective', which have the tendency to recur with the solar rotation period.Key words. Ionosphere (Aural ionosphere; Ionosphere- magnetosphere interactions) · Magnetospheric Physics (current system)

Temporal evolutions of the solar wind conditions at 1 AU prior to the near‐Earth X lines in the tail: Superposed epoch analysis

2016 ◽  
Vol 121 (8) ◽  
pp. 7488-7496 ◽  
Author(s):  
L. Q. Zhang ◽  
L. Dai ◽  
W. Baumjohann ◽  
A. T. Y. Lui ◽  
C. Wang ◽  
...  
Keyword(s):  
Solar Wind ◽  
Superposed Epoch Analysis ◽  
Epoch Analysis

Association of chorus waves and source/seed electrons with the enhancement of relativistic electrons in the outer Van Allen belt

2020 ◽  
Author(s):  
Afroditi Nasi ◽  
Ioannis A. Daglis ◽  
Christos Katsavrias ◽  
Wen Li
Keyword(s):  
Relativistic Electron ◽  
Radiation Belt ◽  
Geomagnetic Disturbance ◽  
Relativistic Electrons ◽  
Outer Radiation Belt ◽  
Inner Magnetosphere ◽  
Superposed Epoch Analysis ◽  
Chorus Waves ◽  
Substorm Activity ◽  
Epoch Analysis

<p>Local acceleration driven by whistler-mode chorus waves is fundamentally important for the acceleration of seed electrons in the outer radiation belt to relativistic energies. Τhis mechanism strongly depends on substorm activity and on the source electron population injected by the substorms into the inner magnetosphere. In our work we use Van Allen Probes data to investigate the features of source electrons, seed electrons and chorus waves for events of enhancement versus events of depletion of relativistic electrons in the outer Van Allen belt. To that end we calculate the electron phase space density (PSD) for five values of the first adiabatic invariant corresponding to source and seed electrons, and we perform a superposed epoch analysis of 28 geomagnetic disturbance events, out of which, 20 result in enhancement and 8 in depletion of relativistic electron PSD. Our results indicate that events resulting in significant enhancement of relativistic electron PSD in the outer radiation belt are characterized by statistically stronger and more prolonged storm and substorm activity, leading to more efficient injections of source but mostly seed electrons to the inner magnetosphere, and also to more pronounced and long-lasting chorus and Pc5 wave activity. The effect of these parameters in the acceleration of electrons seems to be determined by the abundance of seed electrons at the region of L*=4-5.</p>

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