Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Very Large Array Observations of Disturbed Ion Flow from the
  Plasmasphere to the Nighttime Ionosphere   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.

12
The categories of this paper are: nucl-th
9
The categories of this paper are: nlin
34
The categories of this paper are: chem-ph
2
The categories of this paper are: math
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
21
The categories of this paper are: adap-org
30
The categories of this paper are: q-alg
17
The categories of this paper are: q-fin
35
The categories of this paper are: mtrl-th
16
The categories of this paper are: stat
18
The categories of this paper are: econ
22
The categories of this paper are: chao-dyn
4
The categories of this paper are: cond-mat
27
The categories of this paper are: comp-gas
25
The categories of this paper are: patt-sol