GC22B-02
Radiometric Quantification of Aurora Activities during Severe Geomagnetic Storms from SNPP VIIRS Day-Night Band Observations

Tuesday, 15 December 2015: 10:35
3022 (Moscone West)
Xi Shao1, Changyong Cao2, Tung-Chang Liu1, Bin Zhang3, Shing F Fung4 and A Surjalal Sharma5, (1)University of Maryland College Park, College Park, MD, United States, (2)NOAA College Park, College Park, MD, United States, (3)Cooperative Institute for Climate and Satellites University of Maryland, College Park, MD, United States, (4)NASA Goddard Space Flight Ctr, Greenbelt, MD, United States, (5)Univ Maryland, College Park, MD, United States
Abstract:
Two severe geomagnetic storms of level G4 occurred so far in 2015. These are among the strongest geomagnetic storms of the current solar cycle (Solar Cycle 24). Both reached G4-Severe level (Kp = 8) on March 17, 2015 and on June 22, 2015, respectively. The March 17 geomagnetic storm is identified as due to the Coronal Mass Ejections (CMEs) which erupted on March 15 from Region 2297 of solar surface. Combined effects of three CMEs produced on June 18, 19 and 21 caused G4-Severe geomagnetic storm on June 22, 2015. During these geomagnetic storms, solar wind interacts with the Earth's magnetic field and causes temporary disturbances of the Earth's magnetosphere and aurora may be seen in low latitude region.

The Day Night Band (DNB) of the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard Suomi-NPP represents a major advancement in night time imaging capabilities. The DNB senses radiance spanning 7 orders of magnitude in one (0.5-0.9 μm) reflective solar band and provides imagery over illumination levels ranging from full sunlight to quarter moon. In this paper, DNB observations of aurora activities during the two geomagnetic storm events are analyzed. During these events, auroras are observed to evolve with salient features by DNB during orbital pass on the night side (~local time 1:30am) in both hemispheres. The radiometricly calibrated DNB observations allow us to quantitatively analyze the large-scale spatial distribution and temporal evolution of aurora during the geomagnetic storms. The radiance data from DNB observation are collected at the night sides of both hemispheres during the two events and geo-located onto geomagnetic local time (MLT) coordinates. Regions of aurora during each orbital pass are identified through image processing by contouring radiance values and excluding regions with stray light near day-night terminator. The evolution of aurora are characterized with time series of the poleward and low latitude boundary of aurora, their latitude-span and area, peak radiance and total light emission of the aurora region in DNB observation. These characteristic parameters are correlated with solar wind and geomagnetic index parameters. Since DNB imagery has a high spatial resolution (750m), it also allows us to analyze evolution of characteristic spatial distribution of aurora.

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