Quiet time short‐period and day‐to‐day variations in <b>E</b> × <b>B</b> drift studied using 150 km radar echoes from Gadanki

Chaitanya, P. Pavan; Patra, Amit; Rao, S. Vijaya Bhaskara

doi:10.1002/2013ja019668

Cited by 4 publications

(8 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These high‐resolution observations, while presenting the well‐known morphology of forenoon descent and afternoon ascent of the echoing region, illustrate quasiperiodic and sometimes highly complex variations of echo SNR indicating the role of complex forcing on the echoing phenomenon. The quasiperiodicity is found to be 5–15 min consistent with earlier observations from Gadanki (Patra, 2011; Pavan Chaitanya et al, 2014). On some occasions, the echoing region also shows multiple thin layers akin to those observed from Jicamarca (e.g., Chau & Kudeki, 2013).…”

Section: Observational Resultssupporting

confidence: 90%

On the Type‐A and Type‐B 150‐km Radar Echoes

et al. 2020

Self Cite

View full text Add to dashboard Cite

Type-A (weaker and wider Doppler spectra) and Type-B (stronger and narrower Doppler spectra) echoes are inherent to the puzzling 150-km echoing phenomenon. In this paper, we investigate the characteristics and possible origin of the Type-A and Type-B 150-km echoes using high-resolution 53-MHz radar and Digisonde observations from Gadanki. Results show that the Type-A echoes dominate the echoing phenomenon and they always precede the Type-B echoes. Intriguingly, the Type-B echoes are fundamentally not narrower than the Type-A echoes as was originally thought. The primary reason that distinguishes the Type-B echoes from the rest is the confinement of a few high PSD values at the center of the spectra, resulting in narrow spectral width. Spectral spreads of both types of echoes are found to increase with echo signal-to-noise ratio (SNR), and in fact, the spectral spreads of the Type-B echoes are higher than those of the Type-A echoes. Observations also show spectral evolution displaying the occurrence of Type-A and Type-B echoes in tune with the quasiperiodicity in the echo strength (SNR). We propose that both types of echoes primarily are of common origin, presumably linked with naturally enhanced incoherent scattering. Looking at the simultaneously observed short period variations in the lower F region electron density, we propose a gravity wave induced pathway as a plausible mechanism accounting for echo intensity modulation as well as spectral transition.

show abstract

Section: Observational Resultssupporting

confidence: 90%

On the Type‐A and Type‐B 150‐km Radar Echoes

et al. 2020

Self Cite

View full text Add to dashboard Cite

show abstract

“…It is noticed from their observations that, on an average, the vertical drifts are close to 0 or negative ∼1500 LT in June and July months and show decreasing trend around this time. Note that the decreasing trend in afternoon hours in months other than June solstice (e.g., December month) was not observed by both Pavan Chaitanya et al () and Patra et al (). Thus, these case studies give credence to the presence of westward Sq electric fields in afternoon hours during June solstice in solar minimum period.…”

Section: Discussionmentioning

confidence: 73%

“…These measurements have been extensively used over the Peruvian sector (Hui & Fejer, ). Over the Indian sector, such measurements of the vertical drifts over Gadanki (13.5°N, 79.2°E, dip latitude 6.5°N) are reported by Pavan Chaitanya et al () and Patra et al (). Patra et al () reported the vertical drifts for 4 days during July–August 2009 that indicate downward trend at ∼1500 LT. As the radar observational time was limited to ∼1500 LT, the westward Sq electric field could not be ascertained on most of the cases beyond this local time.…”

Section: Discussionmentioning

confidence: 78%

“…Some of the earlier reversals seen in Figure can be accounted by westward electric field similar to this measurement. Further, Pavan Chaitanya et al () reported observations of 150 km echoes during 5 months in 2009 for a few consecutive days in each month. It is noticed from their observations that, on an average, the vertical drifts are close to 0 or negative ∼1500 LT in June and July months and show decreasing trend around this time.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

On the Occurrence of Afternoon Counter Electrojet Over Indian Longitudes During June Solstice in Solar Minimum

et al. 2018

View full text Add to dashboard Cite

Studies made earlier using ground‐based observations of geomagnetic field over the Indian longitudes revealed that the occurrence of equatorial counter electrojet (CEJ) events in afternoon hours is more frequent during June solstice (May‐June‐July‐August) in solar minimum than in other periods. In general, the June solstice solar minimum CEJ events occur between 1500 local time (LT) and 1800 LT with peak strength of about −10 nT at around 1600 LT. In order to understand the frequent occurrence of these CEJ events, an investigation is carried out using an equatorial electrojet model (Anandarao, 1976, https://doi.org/10.1029/GL003i009p00545) and the empirical vertical drift model by Fejer et al. (2008, https://doi.org/10.1029/2007JA012801). The strength, duration, peak value, and the occurrence time of CEJ obtained using electrojet model match remarkably well with the corresponding observation of average geomagnetic field variations. The occurrence of CEJ is found to be due to solar quiet (Sq) electric field in the westward direction which is manifested as downward drift in Fejer et al. (2008, https://doi.org/10.1029/2007JA012801) model output during 1500–1800 LT. Further, the occurrence of afternoon reversal of Sq electric field in this season is shown to be consistent with earlier studies from Indian sector. Therefore, this investigation provides explicit evidence for the role of westward Sq electric field on the generation of afternoon CEJ during June solstice in solar minimum periods over the Indian sector indicating the global nature of these CEJ events.

show abstract

“…These drift values (Patra et al, 2012(Patra et al, , 2014 are larger than the values derived in the present study. Using the same technique as Patra et al (2012Patra et al ( , 2014, the forenoon mean value of vertical drifts were found to be varying around 11-14 and 24-43 m/s during January and February 2009 (Chaitanya et al, 2013(Chaitanya et al, , 2014. For a high solar activity period, Anderson et al (2009) inferred the vertical drift pattern from the EEJ measurements for Indian longitudes during winter solstice and equinoxes.…”

Section: Discussion and Summarymentioning

confidence: 99%

On Estimation of Daytime Equatorial Vertical (E × B) Plasma Drifts Using Optical Neutral Dayglow Emission Measurements

Karan

Pallamraju

2020

JGR Space Physics

View full text Add to dashboard Cite

Vertical drift (E × B) over the geomagnetic equator of the Earth is one of the fundamental parameters that governs the equatorial electrodynamics, which is responsible for the formation of large-scale phenomena in low and equatorial latitudes. We present a novel approach using ground-based optical neutral oxygen dayglow emission intensity measurements to estimate the daytime equatorial vertical drifts. The diurnal patterns of the dayglow emission intensities at OI 557.7, 630.0, and 777.4 nm wavelengths obtained from a low-latitude location, Hyderabad (78.4°E, 17.5°N; 8.9°N MLAT), India, are observed to be symmetric with respect to local noon on some days and asymmetric on some other. The extent of asymmetric nature is characterized by a parameter called Asymmetricity in Time (AT), which shows similar variations with the integrated Equatorial Electrojet (EEJ) strength. AT values obtained from the dayglow measurements are used to infer the vertical drifts. Vertical drifts derived by this method match well with the global climatological model estimates and with radar measurements. This new approach provides an alternative method for obtaining vertical drifts to enable systematic investigations of equatorial electrodynamics. Plain Language SummaryIt is well-known that the ionospheric equatorial zonal electric fields of the Earth play a key role in the generation and development of all the large-scale coupled equatorial-and low-latitude processes. Thus, knowledge of the equatorial electric fields is essential for comprehensive investigations of the equatorial-and low-latitude upper atmospheric behavior. This information on equatorial electric fields can be obtained directly by measuring the vertical drift of plasma above the magnetic equator. The vertical drifts are conventionally measured by ground-based radars and space-based payloads. In this work, a novel technique to estimate the daytime equatorial vertical drifts is presented using ground-based optical dayglow emission measurements. The estimated drifts match well with the model estimates and both ground-and space-borne observations as reported in the published literature. This method of estimating vertical drifts can be used to carry out continuous and systematic investigations of the equatorial electrodynamics. To the best of our knowledge, such a possibility of deriving the daytime equatorial vertical drifts using ground-based optical methods has not been shown before.

show abstract

Quiet time short‐period and day‐to‐day variations in E × B drift studied using 150 km radar echoes from Gadanki

Cited by 4 publications

References 37 publications

On the Type‐A and Type‐B 150‐km Radar Echoes

On the Type‐A and Type‐B 150‐km Radar Echoes

On the Occurrence of Afternoon Counter Electrojet Over Indian Longitudes During June Solstice in Solar Minimum

On Estimation of Daytime Equatorial Vertical (E × B) Plasma Drifts Using Optical Neutral Dayglow Emission Measurements

Contact Info

Product

Resources

About