Electrodynamical response of the Indian low-mid latitude ionosphere to the very large solar flare of 28 October 2003 – a case study

Manju, G.; Pant, Tarun Kumar; Devasia, C. V.; Ravindran, Sudha; Sridharan, R.

doi:10.5194/angeo-27-3853-2009

Cited by 30 publications

(28 citation statements)

References 21 publications

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“…To study the effect of flares on electron density profiles, two kinds of ground‐based instruments, ionosonde and incoherent scatter (IS) radar, are the main candidates. Owing to the short wave fadeout effects, ionosondes can rarely record complete ionograms during flares [e.g., Mendillo et al , 2006; Smithtro et al , 2006; Manju et al , 2009]. Thus IS radar is the only type of ground‐based instrument used in the study of the altitude distribution of the ionospheric response, as noticed by Thome and Wagner [1971] and Mendillo and Evans [1974].…”

Section: Introductionmentioning

confidence: 99%

Ionospheric response to the X-class solar flare on 7 September 2005

et al. 2011

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[1] We investigate the extreme ionospheric effect during the intense solar flare (X17.0/3B) that occurred on 7 September 2005. A strong E region electron density enhancement is observed by the incoherent scatter radars at Millstone Hill, Sondrestrom, and Tromsø, as well as by the radio occultation experiment on board the CHAMP satellite. The observations from both Millstone Hill and Sondrestrom stations show the average percentage enhancements of electron density during 17:40-18:10 UT are more than 200% near the E region peak height but only about 10% near the F region peak height; as a result, it leads to an unusual phenomenon that the E region electron density exceeds the F region electron density. We ascribe the unusual response to weak enhancement in EUV flux and strong enhancement in X-ray flux during this flare. To further understand this unusual feature, we analyze in detail the E region response by comparing the electron production rates derived from the measurements with those fitted by the Chapman production function. Our results demonstrate that the Chapman production theory fits the observations better in the flare time than in the nonflare time, which is attributed to the obvious difference in the solar radiation spectra at flare and nonflare times. Owing to the strong enhancement in X-ray flux during this flare, the E region electron production is more dominated by the X-ray, and the Chapman ionization theory is more applicable in the flare time than in the nonflare time. In addition, we propose a method to estimate the effective solar radiation flux from the ionospheric observations of electron density profiles. The radiation flux derived with our method agrees well with the X-ray flux at 0.1-0.8 nm observed by GOES-12.

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Section: Introductionmentioning

confidence: 99%

Ionospheric response to the X-class solar flare on 7 September 2005

et al. 2011

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“…The variations of geomagnetic H component induced by different solar flares are different. The temporal evolutions of H component in the two stations are consistent with that in Trivandrum and Annamalainagar over Indian sector during the X2.4 solar flare on 29 March 1991 and not in good agreement with that in the above two stations of India during the X17.2 flare on 28 October 2003 [ Manju and Viswanathan , ; Manju et al ., ]. As shown in Figure c, the strength of EEJ is always positive and around 68 nT before the flare.…”

Section: Resultsmentioning

confidence: 81%

“…Manju et al . [] presented the flux enhancements induced by solar flare over different longitude sectors produce different variations in EEJ strength. Dmitriev and Yeh [] used the geomagnetic data to study the great X‐class solar flares on 14 July 2000 and on 28 October 2003.…”

Section: Introductionmentioning

confidence: 99%

Response of the American equatorial and low‐latitude ionosphere to the X1.5 solar flare on 13 September 2005

Xiong

Wan

et al. 2014

JGR Space Physics

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Based on the coordinated observations by the incoherent scatter radar (ISR), ionosonde, magnetometers, and GPS receivers, the electrodynamic effects on the equatorial and low-latitude ionosphere have been investigated during the intense solar flare (X1.5/2B) on 13 September 2005. In the initial stage of the flare, the ISR and ionosonde measurements at Jicamarca show the decreases of 10.14 m/s and 20 km in the upward vertical E × B drift velocity and the F 2 region peak height, respectively, while equatorial electrojet (EEJ) strength over American sector indicates a sudden increase of 53.7 nT. The decrease of the upward vertical E × B drift velocity reveals the weakening of eastward electric field during the flare, which is firstly and directly observed by instrument. It is well known that the variation of equatorial electric field is mainly attributed to the ionospheric dynamo electric field and partially affected by the penetration of interplanetary electric field. The observations during this flare suggest that the flare-induced increase of Cowling conductivity changes the ionospheric dynamo electric field and further results in the weakening of eastward electric field and the decrease of the upward vertical E × B drift velocity. Meanwhile, the upward vertical E × B drift velocity and the EEJ strength during the flare are negatively correlated, which is contrary to the knowledge established by Anderson et al. (2002) based on 10 days of observations in the Peruvian longitude sector. The difference may be caused by the flare-induced enhancement of Cowling conductivity. In addition, GPS total electron content (TEC) observations from six stations in the American equator and low latitudes show an enhancement of 1.47-3.09 TEC units. The measurements of GPS and ISR indicate that the contribution of the enhanced photoionization to the increase of TEC is more than that of electrodynamic effect during the initial stage of the intense flare. IntroductionAs one of the severest solar events, the solar flare is an important topic of solar-terrestrial relations and current space weather research. During a flare, the large and rapid increases of solar X-ray and extreme ultraviolet (EUV) enhance the ionization of the upper atmosphere and cause many kinds of sudden ionospheric disturbances (SIDs). Since 1960s, many researchers have studied different kinds of SIDs, such as sudden cosmic noise absorption (SCNA), sudden enhancement of atmospheric (SEA), sudden phase anomaly (SPA), short wave fadeout (SWF), sudden frequency deviation (SFD), and sudden increase of total electron content (SITEC) [Garriott et al., 1967;Sao et al., 1970;Stonehocker, 1970;Donnelly, 1971;Jones, 1971;Ohshio, 1971;Deshpande and Mitra, 1972;Davies, 1980;Wan et al., 2005]. Previous works have suggested that different disturbed phenomena are attributed to the increase of electron density at different altitudes of ionosphere during flares [e.g., Mendillo and Evans, 1974;Le et al., 2007;Xiong et al., 2011]. The SCNA, SEA, SPA, and SWF are closely relat...

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“…These disturbances are observed in the form of sudden increases in the ionospheric electron density in the D, E and F regions, reflecting in the ionospheric currents (Curto et al 1994a, b, Xiong et al, 2011Tsurutani et al, 2005;Manju et al, 2009;Nogueira et al, 2015;Abdu et al, 2017). The equatorial electrojet (EEJ) current system is also disturbed due to sudden increase in the solar ionizing radiation flux.…”

Section: Introductionmentioning

confidence: 99%

Latitude-dependent delay in the responses of the equatorial electrojet and Sq currents to X-class solar flares

Nogueira¹,

Abdu²,

Souza³

et al. 2018

Ann. Geophys.

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Abstract. We have analyzed low-latitude ionospheric current responses to two intense (X-class) solar flares that occurred on 13 May 2013 and 11 March 2015. Sudden intensifications, in response to solar flare radiation impulses, in the S q and equatorial electrojet (EEJ) currents, as detected by magnetometers over equatorial and low-latitude sites in South America, are studied. In particular we show for the first time that a 5 to 8 min time delay is present in the peak effect in the EEJ, with respect that of S q current outside the magnetic equator, in response to the flare radiation enhancement. The S q current intensification peaks close to the flare X-ray peak, while the EEJ peak occurs 5 to 8 min later. We have used the Sheffield University Plasmasphere-Ionosphere Model at National Institute for Space Research (SUPIM-INPE) to simulate the E-region conductivity enhancement as caused by the flare enhanced solar extreme ultraviolet (EUV) and soft Xrays flux. We propose that the flare-induced enhancement in neutral wind occurring with a time delay (with respect to the flare radiation) could be responsible for a delayed zonal electric field disturbance driving the EEJ, in which the Cowling conductivity offers enhanced sensitivity to the driving zonal electric field.

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Electrodynamical response of the Indian low-mid latitude ionosphere to the very large solar flare of 28 October 2003 – a case study

Cited by 30 publications

References 21 publications

Ionospheric response to the X-class solar flare on 7 September 2005

Ionospheric response to the X-class solar flare on 7 September 2005

Response of the American equatorial and low‐latitude ionosphere to the X1.5 solar flare on 13 September 2005

Latitude-dependent delay in the responses of the equatorial electrojet and <i>S</i><sub><i>q</i></sub> currents to X-class solar flares

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Electrodynamical response of the Indian low-mid latitude ionosphere to the very large solar flare of 28 October 2003 – a case study

Cited by 30 publications

References 21 publications

Ionospheric response to the X-class solar flare on 7 September 2005

Ionospheric response to the X-class solar flare on 7 September 2005

Response of the American equatorial and low‐latitude ionosphere to the X1.5 solar flare on 13 September 2005

Latitude-dependent delay in the responses of the equatorial electrojet and &lt;i&gt;S&lt;/i&gt;&lt;sub&gt;&lt;i&gt;q&lt;/i&gt;&lt;/sub&gt; currents to X-class solar flares

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Latitude-dependent delay in the responses of the equatorial electrojet and <i>S</i><sub><i>q</i></sub> currents to X-class solar flares