Very Large Array Observations of Disturbed Ion Flow from the Plasmasphere to the Nighttime Ionosphere

Abstract

We present the results of a multi-scale analysis of TEC fluctuations using a roughly five-hour observation of the bright radio source Virgo A with the Very Large Array (VLA) at 74 MHz in its B configuration. Our analysis combines data sensitive to fine-scale structure (~10 km and <0.001 TECU in amplitude) along the line of sight to Virgo A as well as larger structures (hundreds of km) observed using several (~30) moderately bright sources in the field of view. The observations span a time period from midnight to dawn local time during 1 March 2001. Several groups of magnetic eastward directed (MED), wavelike disturbances were identified and determined to be located within the plasmasphere (2.1<L<2.9). We have also detected evidence of non-wavelike structures associated with these disturbances which are propagating roughly toward magnetic north. These likely represent a non-uniform density flow from the plasmasphere toward the nighttime ionosphere. AE and Kp indices and GPS TEC data indicate that during the observations, there were low levels of geomagnetic activity accompanied by somewhat localized depletions in ionospheric density. Thus, the observed plasmaspheric disturbance may be part of a flow triggered by these ionospheric depletions, likely associated with forcing from the lower atmosphere which is typically more prominent during quiet geomagnetic conditions. In addition, we have also observed several roughly westward directed and southeast directed waves located within the ionosphere. They are coincident in time with the plasmaspheric disturbances and may be related to the deposition of material onto the nighttime ionosphere.

accepted to Radio Science

References in corpus (6)

• The VLA Low-frequency Sky Survey
• The 74MHz System on the Very Large Array
• Probing Fine-Scale Ionospheric Structure with the Very Large Array Radio Telescope
• High-precision Measurements of Ionospheric TEC Gradients with the Very Large Array VHF System
• A new approach to mitigation of radio frequency interference in interferometric data
• A New Technique for Spectral Analysis of Ionospheric TEC Fluctuations Observed with the Very Large Array VHF System: From QP Echoes to MSTIDs

Cited by in corpus (9)

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• Density duct formation in the wake of a travelling ionospheric disturbance: Murchison Widefield Array observations
• Insights into the nature of northwest-to-southeast aligned ionospheric wavefronts from contemporaneous Very Large Array and ionosondes observations
• Advanced spectral analysis of ionospheric waves observed with sparse arrays
• Ionospheric observations of Underground Nuclear Explosions (UNE) using GPS and the Very Large Array
• A new angle for probing field-aligned irregularities with the Murchison Widefield Array