Modeling seasonal variations of auroral particle precipitation in a global-scale magnetosphere-ionosphere simulation

2009 ◽  
Vol 114 (A1) ◽  
pp. n/a-n/a ◽  
Author(s):  
M. Wiltberger ◽  
R. S. Weigel ◽  
W. Lotko ◽  
J. A. Fedder
Keyword(s):  
Seasonal Variations ◽  
Global Scale ◽  
Particle Precipitation ◽  
Auroral Particle Precipitation

scholarly journals Strong sunward propagating flow bursts in the night sector during quiet solar wind conditions: SuperDARN and satellite observations

2002 ◽  
Vol 20 (6) ◽  
pp. 771-779 ◽  
Author(s):  
C. Senior ◽  
J.-C. Cerisier ◽  
F. Rich ◽  
M. Lester ◽  
G. K. Parks
Keyword(s):  
Convective Transport ◽  
High Time Resolution ◽  
Polar Cap ◽  
Particle Precipitation ◽  
Phase Velocities ◽  
Plasma Injection ◽  
Night Side ◽  
Magnetospheric Boundaries ◽  
Auroral Particle Precipitation ◽  
Imf Clock Angle

Abstract. High-time resolution data from the two Iceland SuperDARN HF radars show very strong nightside convection activity during a prolonged period of low geomagnetic activity and northward interplanetary magnetic field (IMF). Flows bursts with velocities ranging from 0.8 to 1.7 km/s are observed to propagate in the sunward direction with phase velocities up to 1.5 km/s. These bursts occur over several hours of MLT in the 20:00–01:00 MLT sector, in the evening-side sunward convection. Data from a simultaneous DMSP pass and POLAR UVI images show a very contracted polar cap and extended regions of auroral particle precipitation from the magnetospheric boundaries. A DMSP pass over the Iceland-West field-of-view while one of these sporadic bursts of enhanced flow is observed, indicates that the flow bursts appear within the plasma sheet and at its outward edge, which excludes Kelvin-Helmholtz instabilities at the magnetopause boundary as the generation mechanism. In the nightside region, the precipitation is more spot-like and the convection organizes itself as clockwise U-shaped structures. We interpret these flow bursts as the convective transport following plasma injection events from the tail into the night-side ionosphere. We show that during this period, where the IMF clock angle is around 70°, the dayside magnetosphere is not completely closed.Key words. Ionosphere (Auroral ionosphere; Ionospheremagnetosphere interactions; Particle precipitation)

scholarly journals Convective–Stratiform Precipitation Variability at Seasonal Scale from 8 Yr of TRMM Observations: Implications for Multiple Modes of Diurnal Variability

2008 ◽  
Vol 21 (16) ◽  
pp. 4087-4114 ◽  
Author(s):  
Song Yang ◽  
Eric A. Smith
Keyword(s):  
Seasonal Variations ◽  
Seasonal Variability ◽  
Regional Scale ◽  
Tropical Rainfall Measuring Mission ◽  
Global Scale ◽  
Total Rainfall ◽  
Diurnal Variability ◽  
Multiple Modes ◽  
Late Evening ◽  
Stratiform Rainfall

Abstract This study investigates the variability of convective and stratiform rainfall from 8 yr (1998–2005) of Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) and TRMM Microwave Imager (TMI) measurements, focusing on seasonal diurnal variability. The main scientific goals are 1) to understand the climatological variability of these two dominant forms of precipitation across the four cardinal seasons and over continents and oceans separately and 2) to understand how differences in convective and stratiform rainfall variations ultimately determine how the diurnal variability of the total rainfall is modulated into multiple modes. There are distinct day–night differences for both convective and stratiform rainfall. Oceanic (continental) convective rainfall is up to 25% (50%) greater during nighttime (daytime) than daytime (nighttime). The seasonal variability of convective rainfall’s day–night difference is relatively small, while stratiform rainfall exhibits very apparent day–night variations with seasonal variability. There are consistent late evening diurnal peaks without obvious seasonal variations over ocean for convective, stratiform, and total rainfall. Over continents, convective and total rainfall exhibit consistent dominant afternoon peaks with little seasonal variations—but with late evening secondary peaks exhibiting seasonal variations. Stratiform rainfall over continents exhibits a consistent strong late evening peak and a weak afternoon peak, with the afternoon mode undergoing seasonal variability. Thus, the diurnal characteristics of stratiform rainfall appear to control the afternoon secondary maximum of oceanic rainfall and the late evening secondary peak of continental rainfall. Even at the seasonal–regional scale spatially or the interannual global scale temporally, the secondary mode can become very pronounced, but only on an intermittent basis. Overall, the results presented here demonstrate the importance of partitioning the total rainfall into convective and stratiform components and suggest that diurnal modes largely arise from distinct diurnal stratiform variations modulating convective variations.

scholarly journals The driving mechanisms of particle precipitation during the moderate geomagnetic storm of 7 January 2005

2007 ◽  
Vol 25 (9) ◽  
pp. 2053-2068 ◽  
Author(s):  
N. Longden ◽  
F. Honary ◽  
A. J. Kavanagh ◽  
J. Manninen
Keyword(s):  
Solar Wind ◽  
Geomagnetic Storm ◽  
Geomagnetic Activity ◽  
Dynamic Pressure ◽  
Energetic Electron ◽  
Recovery Phase ◽  
Global Scale ◽  
Electron Precipitation ◽  
Particle Precipitation ◽  
Substorm Activity

Abstract. The arrival of an interplanetary coronal mass ejection (ICME) triggered a sudden storm commencement (SSC) at ~09:22 UT on the 7 January 2005. The ICME followed a quiet period in the solar wind and interplanetary magnetic field (IMF). We present global scale observations of energetic electron precipitation during the moderate geomagnetic storm driven by the ICME. Energetic electron precipitation is inferred from increases in cosmic noise absorption (CNA) recorded by stations in the Global Riometer Array (GLORIA). No evidence of CNA was observed during the first four hours of passage of the ICME or following the sudden commencement (SC) of the storm. This is consistent with the findings of Osepian and Kirkwood (2004) that SCs will only trigger precipitation during periods of geomagnetic activity or when the magnetic perturbation in the magnetosphere is substantial. CNA was only observed following enhanced coupling between the IMF and the magnetosphere, resulting from southward oriented IMF. Precipitation was observed due to substorm activity, as a result of the initial injection and particles drifting from the injection region. During the recovery phase of the storm, when substorm activity diminished, precipitation due to density driven increases in the solar wind dynamic pressure (Pdyn) were identified. A number of increases in Pdyn were shown to drive sudden impulses (SIs) in the geomagnetic field. While many of these SIs appear coincident with CNA, SIs without CNA were also observed. During this period, the threshold of geomagnetic activity required for SC driven precipitation was exceeded. This implies that solar wind density driven SIs occurring during storm recovery can drive a different response in particle precipitation to typical SCs.

scholarly journals Auroral particle precipitation characterized by the substorm cycle

2013 ◽  
Vol 118 (3) ◽  
pp. 1022-1039 ◽  
Author(s):  
Simon Wing ◽  
Matina Gkioulidou ◽  
Jay R. Johnson ◽  
Patrick T. Newell ◽  
Chih-Ping Wang
Keyword(s):  
Particle Precipitation ◽  
Auroral Particle Precipitation
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