Nighttime Mid-Latitude Travelling Ionospheric Disturbances Associated with Mild Spread-F Conditions.

Bowman, G. G.

doi:10.5636/jgg.43.899

Cited by 17 publications

(13 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The F2-layer frontal structures (bands) reported by Behnke (1979) from a northern-hemisphere mid-latitude location are moving in south-west directions. As travel speeds and structure spacings are consistent with those reported by McNicol et al (1956) and Bowman (1960aBowman ( , 1991b, it is possible that these are moving spread-F structures. However Behnke suggests "that these bands are manifestations of the so-called 'Perkins' instability" (Perkins, 1973).…”

Section: Discussionsupporting

confidence: 84%

“…Evidence is now being found to suggest that the FAIs recorded at Es-layer levels by the MU-radar are associated with MS-TIDs (Woodman etal., 1991;Yamamoto etal.,1993Yamamoto etal., ,1994Tsunoda etal.,1994). TheE5-layer level FAIs recorded in Japan at 25 MHz, by Tanaka and Venkateswaran (1982) were found to be travelling in west to southwest directions with speeds comparable with those of nighttime F2-layer MS-TIDs (Bowman, 1991b).…”

Section: Some Characteristics Of Nighttime Medium-scale Travelling Iomentioning

confidence: 84%

“…Thus spread-F associated F2-layer macroscale changes (particularly the height suppression) seem to be coupled to sporadic-E enhancements recorded sometime after the height suppression, the time delay depending on the F2-layer slopes lines. Also it is now known that these F2-region movements are produced by the arrival of MS-TIDs which consist of wavetrains with periodicities around 15 minutes (Bowman and Monro, 1988;Bowman, 1991aBowman, , 1991b. These wavetrains modulate the isoionic contours while these height changes are occurring.…”

Section: Some Characteristics Of Nighttime Medium-scale Travelling Iomentioning

confidence: 99%

See 2 more Smart Citations

MU-Radar Recorded Field-Aligned Irregularities in the F2 Region and Associated Sporadic-E Disturbances.

Bowman

Fukao

Yamamoto

et al. 1994

J. geomagn. geoelec

Self Cite

View full text Add to dashboard Cite

Recordings by the MU-radar of two ionospheric events involving F2-layer field-aligned irregularities (FAIs) on one particular night in a sunspot-maximum period (July 24/25, 1991) have been examined and compared with ionospheric events deduced from the analyses of ionograms from the adjacent ionosonde stations of Akita and Kokubunji. Ionograms from three other Japanese stations have also been analysed. The analyses detected two medium-scale travelling ionospheric disturbances (MSTIDs) which pass through the MU-radar observing region at times close to those of the FAI recordings. The MS-TIDs seem to be propagating at both F2-layer and ES layer levels. F2-layer macroscale changes and E. -layer enhancement (particularly the ES enhancements) have been used to track the disturbances over significant distances from Wakkanai in the north to Yamagawa in the south, and even to the island of Okinawa (located some 2,500 km from Wakkanai). Spread-F is recorded during the passage of these MS-TIDs, but only at some stations. Quite apart from the apparent association of these MS-TIDs with the FAI recordings, these results would seem to reinforce other results which indicate an association between macroscale F2-layer height changes and enhanced sporadic-E occurrence.

show abstract

Section: Discussionsupporting

confidence: 84%

Section: Some Characteristics Of Nighttime Medium-scale Travelling Iomentioning

confidence: 84%

Section: Some Characteristics Of Nighttime Medium-scale Travelling Iomentioning

confidence: 99%

See 1 more Smart Citation

MU-Radar Recorded Field-Aligned Irregularities in the F2 Region and Associated Sporadic-E Disturbances.

Bowman

Fukao

Yamamoto

et al. 1994

J. geomagn. geoelec

Self Cite

View full text Add to dashboard Cite

show abstract

“…The AU index [Allen and Kroehl, 1975, Figure 5] has a well-defined maximum near 1800 LT (these results are also given by Mayaud [1980]). Thus it is suggested that the negative association (illustrated in Figures 1 and 4 [Bowman, 1990[Bowman, , 1991b[Bowman, , 1991c. Figure 12 of Bowman [1990] illustrates these relationships where the foF2 reduction is about 1 MHz.…”

Section: Discussionmentioning

confidence: 99%

Short‐term delays (hours) of ionospheric spread F occurrence at a range of latitudes, following geomagnetic activity

Bowman¹

1998

J. Geophys. Res.

Self Cite

View full text Add to dashboard Cite

Abstract. The analyses have investigated the short-term responses of spread F occurrence (as identified on ionograms) at low-and middle-latitude stations to geomagnetic activity changes so that comparisons can be made with results from equatorial stations reported earlier [Bowman, 1995]. Using superposed-epoch methods, it is found that the AE index is either enhanced or depressed a few hours prior to spread F occurrence depending on whether or not low or high (respectively) spread F controls are used. The geomagnetic activity related to this inverse relationship is centered mainly around the local times of 1200 and 1800. A direct relationship is also found for geomagnetic activity which occurs in the night hours. The results for these other latitude stations are the same as those reported in the earlier paper Ibr equatorial stations. This paper also considers for the equatorial station Huancayo extreme responses of spread F occurrence to geomagnetic activity, involving occasions of high spread F occurrence when there is a sudden drop in the level to zero for isolated days when a few hours earlier at the favored times mentioned above enhanced geomagnetic activity occurs. It is suggested that the inverse relationship involves the control of medium-scale traveling ionospheric disturbance (MS-TID) wave amplitudes by neutral-density changes, produced by large-scale traveling ionospheric disturbances (LS-TIDs) generated by geomagnetic activity concentrated mainly around the local times of 1200 and 1800. The LS-TIDs generated by geomagnetic activity at night behave differently. Height rises are produced, and as a result of the lower neutral-density levels, spread F is recorded particularly in the presunrise period. Extending the comparison of spread F characteristics at different latitudes, some comments are made on recent observations using data from satellite recordings, concerning the similarities between electron-density depletions detected for equatorial regions and those for other regions (e.g., midlatitude regions.)

show abstract

“…On Fig. 1(b) three duplicate traces produced by tilted isoionic surfaces approximately 45 km apart (Bowman, 1991a) are clearly visible. The trace identified by the symbol B results from radiowaves reflected from an isoionic surface tilted about 43 degrees from the horizontal.…”

Section: Introductionmentioning

confidence: 98%

Short-Term Delays in the Occurrence of Mid-Latitude Ionospheric Disturbances Following Other Geophysical and Solar Events.

Bowman

1994

J. geomagn. geoelec

Self Cite

View full text Add to dashboard Cite

Five years of ionograms recorded at a mid-latitude station, Moggill (near Brisbane, Australia) have been examined to determine days of high and days of low activity for 3 ionospheric disturbance parameters. These are nighttime spread-F, daytime first-hop distortions and daytime second-hop spread. Superposed-epoch analyses using these days as controls show that statistically above-average occurrence levels for these parameters can be expected for low geomagnetic activity a few hours before the recording periods for these parameters. Conversely when geomagnetic activity is high a few hours earlier the occurrence levels of these parameters are suppressed. Also, a 3 day delay after enhanced geomagnetic activity at specific local times (reported earlier) is also illustrated and discussed. When mid-latitude spread-F occurrence levels are considered on a global scale it is found that changes in the levels of occurrence are in antiphase with the 10.7 cm solar flux, in particular the 27-day variation due to the solar rotation.It seems likely that these relationships with geomagnetic activity and the 10.7 cm solar flux can be explained in terms of the upper-atmosphere neutral-particle density (UA-NPD) changes which are associated with these geophysical parameters. It is argued that the UA-NPD changes modulate the wave amplitudes of the medium-scale travelling ionospheric disturbances in such a way that large wave amplitudes (needed for significant disturbance conditions) result from lower levels of the UA-NPD. The results suggest that further work on these short term relationships may in the future facilitate the shortterm forecasting of mid-latitude disturbance conditions.

show abstract

Nighttime Mid-Latitude Travelling Ionospheric Disturbances Associated with Mild Spread-F Conditions.

Cited by 17 publications

References 26 publications

MU-Radar Recorded Field-Aligned Irregularities in the F2 Region and Associated Sporadic-E Disturbances.

MU-Radar Recorded Field-Aligned Irregularities in the F2 Region and Associated Sporadic-E Disturbances.

Short‐term delays (hours) of ionospheric spread F occurrence at a range of latitudes, following geomagnetic activity

Short-Term Delays in the Occurrence of Mid-Latitude Ionospheric Disturbances Following Other Geophysical and Solar Events.

Contact Info

Product

Resources

About