Mid-latitude ionospheric scintillation anomaly in the Far East

Abstract

Abstract.A long-term (over 3 years) study has been undertaken to obtain a comprehensive evaluation of VHF ionospheric scintillation morphology in East Asia (at Kokobunji in Japan), using amplitude records from Transit satellites. It is now evident that summer day and night scintillation enhancement in this mid-latitude region is a long-term evidence of a well-known Asian ionospheric disturbance anomaly. The scintillation activity is particularly strong during summer nights (21:00-24:00 LT) and on occasion, all satellite passes recorded on consecutive days are associated with pronounced scintillation activity. A second sub-maximum is observed in the summer pre-noon period (09:00-12:00 LT). The scintillation regions extend latitudinally for a distance of 400-600 km in the F-region and 100-200 km in the Eregion, mostly equatorwards of Kokobunji. For comparison similar scintillation data obtained for one year at the same longitudinal sector but in southern mid-latitudes (Brisbane in Australia) were compared with the simultaneous northern scintillation data. The scintillation activity at Brisbane was much less pronounced in the southern summer but was of the same low level during other seasons as that for Kokobunji. This consistent scintillation anomaly, as yet, has not been included in the global scintillation models, which are essential for radio-satellite communications.

A Study of Daytime L‐Band Scintillation in Association With Sporadic E Along the Magnetic Dip Equator

“…This theory has proven to work well in the midlatitude, where the inclination angle (I) is steep enough to produce Es layers (Whitehead, , ). Evidence regarding the midlatitude (Hajkowicz, , ; Hajkowicz & Minakoshi, ; Ogawa, Suzuki, & Kunitake, ), low latitude, and equatorial regions (Alfonsi et al, ; Huang, ; Kumar et al, ; Patel et al, , ; Seif et al, , , , ; Zou & Wang, ; Zou, ) have shown correlation between the occurrence of daytime scintillation and the Es layer. Nevertheless, thus far, very little is known about the nature of daytime L‐band scintillations and characteristics of Es at the magnetic dip equator, where wind shear theory fails to operate.…”

Characteristics of low latitude ionospheric E-region irregularities linked with daytime VHF scintillations measured from Varanasi

“…Daytime scintillations are seen to be a regular phenomenon in ATS 6 beacons (41 MHz and 140 MHz) recorded at Huancayo, Peru, near magnetic equator (Basu et al 1977). Recently, Hajkowicz and Minakoshi (2003) have made a comprehensive evaluation of VHF ionospheric scintillation morphology in East Asia (Kokobunji, Japan) and concluded that daytime scintillations are due to the occurrence of E s .…”

“…The night-time scintillations are mainly attributed to spread-F, whereas daytime scintillations are linked to E-region irregularities (Anastassiadis et al 1970;DasGupta and Kersley 1976;Rastogi and Iyer 1976;Basu et al 1977;Ogawa et al 1989;Hajkowicz and Minakoshi 2003). Aarons and Whitney (1968) considered the daytime scintillations observed at Sangamore hill (dip 73 • N) to be due to sporadic-E (E s ) cloud and estimated the horizontal dimension to be 300-600 km.…”

Observations of quiet-time moderate midlatitude L-band scintillation in association with plasma bubbles

“…A number of midlatitude scintillation studies have been carried out mainly using the VHF radio transmissions from geostationary satellites, as lower frequencies are more severely affected (Kersley et al 1980;Hajkowicz and Minakoshi 2003). Using a 5-year data set from 150 MHz radio transmissions, Hajkowicz (1994) reported that localized midlatitude scintillation patches frequently occur during sunspot minimum, in association with the occurrence of midlatitude spread F. The observations of L-band scintillation at midlatitudes are mostly reported during severe geomagnetic storms (Ogawa and Kumagai 1985;Bust et al 1997;Ma and Maruyama 2006) and during the equatorward movement of the ionospheric trough along with a storm time-enhanced density (SED) (Ledvina et al 2002).…”