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Research paper thumbnail of Seasonal and diurnal variation of lightning activity over southern Africa and correlation with European whistler observations

Annales Geophysicae, 2006

Research paper thumbnail of Seasonal and Diurnal Variations of Lightning Activity Over West Sumatra and Its Correlation with Precipitation Type

Makara Journal of Science

Seasonal and diurnal variations of lightning activity over West Sumatra have been investigated us... more Seasonal and diurnal variations of lightning activity over West Sumatra have been investigated using observations of Tropical Rainfall Measuring Mission-Lightning Imaging Sensor (TRMM-LIS) over a 16-year period. This study also used TRMM 3B43 and 2A25 data to observe the correlation between lightning activity with rainfall and precipitation type. Results show that lightning occurs more frequently over land than over ocean and coastal areas, in contrast to total rainfall, which is higher over ocean and coastal areas. The lightning pattern is similar to the convective rainfall (particularly deep convective) pattern, which indicates that the majority of lightning in West Sumatra is associated with deep convective rain. The lightning intensity in Indonesia during the convection period, namely, December-January-February and September-October-November, is higher than that during other periods. The diurnal cycle of lightning coincides with the diurnal cycle of cloud migration from the ocean to inland Sumatra, as reported in previous research. Lightning and deep convective precipitation are dominant during the day and evening (16.00-20.00 Local Standard Time [LST]), particularly over land. Stratiform precipitation occurs more frequently from afternoon to early morning (16.00-04.00 LST) over land and at 00.00-12.00 LST over the ocean. Abstrak Variasi Musiman dan Diurnal Petir di Sumatera Barat dan Korelasinya dengan Tipe Hujan. Variasi musiman dan diurnal petir di Sumatera Barat telah diteliti menggunakan data Tropical Rainfall Measuring Mission-Lightning Imaging Sensor (TRMM-LIS) selama 16 tahun. Penelitian ini juga menggunakan data TRMM 3B43 dan 2A25 untuk melihat hubungan antara petir dengan curah hujan dan tipe hujan. Hasil penelitian menunjukkan bahwa petir lebih sering terjadi di daratan daripada di lautan dan pantai berbeda dengan total curah hujan. Pola petir sama dengan pola curah hujan konkevtif khususnya hujan konvektif dalam (deep convective) yang menandakan bahwa mayoritas petir di Sumatera Barat diikuti oleh hujan konvektif dalam. Intensitas petir di Indonesia selama periode konveksi yaitu Desember-Januari-Februari dan September-Oktober-November lebih tinggi daripada periode lainnya.Pola diurnal petir di Sumatera Barat bertepatan dengan pola pergerakan awan dari lauatan ke daratan Sumatera, sebagaimana dilaporkan oleh penelitian sebelumnya. Petir dan hujan konvektif dalam dominan terjadi pada siang dan malam hari (16.00-20.00 WIB), khususnya di daratan. Hujan stratiform lebih sering terjadi pada sore hingga dini hari (16.00-04.00 WIB) di daratan dan 00.000-12.00 WIB di lautan.

Research paper thumbnail of A satellite study of the mid-latitude trough in electron density and VLF radio emission during the magnetic storm of 25 - 27 May 1967

J Atmos Sol Terr Phys, 1973

ABSTRACT

Research paper thumbnail of Modelling and analysis of substorm-related chorus events

The substorm-related chorus event is a recognised VLF signature of the substorm expansion phase. ... more The substorm-related chorus event is a recognised VLF signature of the substorm expansion phase. Computer simulations support the contention that these events are generated by cyclotron resonance between whistler mode waves and energetic electrons which drift into a ground station's field of view from an injection site near midnight.

Research paper thumbnail of Whistler-lightning correlations: tetrachoric index and similarity measures

Research paper thumbnail of Lightning here, whistlers there

Research paper thumbnail of Departures from sinusoidal variation in the occurrence of lightning in Equatorial Africa

Research paper thumbnail of Digital VLF Recording and Analysis System for SANAE--IV

Research paper thumbnail of Overview of VLF Radio Wave Activity at SANAE IV During 2002

Research paper thumbnail of Role of Anisotropy in the Simulation of Substorm Chorus Events

Research paper thumbnail of A Simple Model for Wave Growth Leading to Substorm Chorus Events

Research paper thumbnail of SANAE Observations of Substorm-Related Chorus Events

Research paper thumbnail of Seasonal and diurnal variations in lightning over Southern Africa and the effect of warm ocean currents

Research paper thumbnail of Whistler-lightning correlations: tetrachoric index and similarity measures

Research paper thumbnail of Sinusoidal Variation of Lightning Activity over Africa

Research paper thumbnail of Co-ordinated Observations of Sprites

Research paper thumbnail of The Conjugate Sprite Campaign---A potential north-south collaborative project for the International Heliophysical Year

Research paper thumbnail of The Conjugate Sprite Campaign: A Potential North-South Collaborative Project for the IHY

Red sprites are luminous phenomena which occur at high altitude above thunderstorms. It is though... more Red sprites are luminous phenomena which occur at high altitude above thunderstorms. It is thought that a beam of relativistic electrons may be generated during the formation of a red sprite and that this beam should travel along a magnetic field line to the conjugate hemisphere. A campaign was organised to detect evidence of this energetic electron beam. During the

Research paper thumbnail of Simulation of substorm chorus events

The Substorm Chorus Event (SCE) is a VLF radio phenomenon which may be observed after the onset o... more The Substorm Chorus Event (SCE) is a VLF radio phenomenon which may be observed after the onset of the substorm expansion phase. It consists of a band of VLF chorus emissions with rising upper and lower cutoff frequencies. These emissions arise from cyclotron resonance between whistler mode waves and energetic electrons which drift into a station's field of view from an injection site around midnight. Particle tracking simulations are used to understand the nature of these events. Specifically, consideration of changes in the degree of anisotropy of the particles within a station's field of view and the resulting implications for cyclotron resonance instability produce simulated events in good agreement with observations.

Research paper thumbnail of First observations of Trimpi Events at Durban ( L = 1.69) using an OMSKI Receiver

Journal of Geophysical Research, 1993

ABSTRACT

Research paper thumbnail of Seasonal and diurnal variation of lightning activity over southern Africa and correlation with European whistler observations

Annales Geophysicae, 2006

Research paper thumbnail of Seasonal and Diurnal Variations of Lightning Activity Over West Sumatra and Its Correlation with Precipitation Type

Makara Journal of Science

Seasonal and diurnal variations of lightning activity over West Sumatra have been investigated us... more Seasonal and diurnal variations of lightning activity over West Sumatra have been investigated using observations of Tropical Rainfall Measuring Mission-Lightning Imaging Sensor (TRMM-LIS) over a 16-year period. This study also used TRMM 3B43 and 2A25 data to observe the correlation between lightning activity with rainfall and precipitation type. Results show that lightning occurs more frequently over land than over ocean and coastal areas, in contrast to total rainfall, which is higher over ocean and coastal areas. The lightning pattern is similar to the convective rainfall (particularly deep convective) pattern, which indicates that the majority of lightning in West Sumatra is associated with deep convective rain. The lightning intensity in Indonesia during the convection period, namely, December-January-February and September-October-November, is higher than that during other periods. The diurnal cycle of lightning coincides with the diurnal cycle of cloud migration from the ocean to inland Sumatra, as reported in previous research. Lightning and deep convective precipitation are dominant during the day and evening (16.00-20.00 Local Standard Time [LST]), particularly over land. Stratiform precipitation occurs more frequently from afternoon to early morning (16.00-04.00 LST) over land and at 00.00-12.00 LST over the ocean. Abstrak Variasi Musiman dan Diurnal Petir di Sumatera Barat dan Korelasinya dengan Tipe Hujan. Variasi musiman dan diurnal petir di Sumatera Barat telah diteliti menggunakan data Tropical Rainfall Measuring Mission-Lightning Imaging Sensor (TRMM-LIS) selama 16 tahun. Penelitian ini juga menggunakan data TRMM 3B43 dan 2A25 untuk melihat hubungan antara petir dengan curah hujan dan tipe hujan. Hasil penelitian menunjukkan bahwa petir lebih sering terjadi di daratan daripada di lautan dan pantai berbeda dengan total curah hujan. Pola petir sama dengan pola curah hujan konkevtif khususnya hujan konvektif dalam (deep convective) yang menandakan bahwa mayoritas petir di Sumatera Barat diikuti oleh hujan konvektif dalam. Intensitas petir di Indonesia selama periode konveksi yaitu Desember-Januari-Februari dan September-Oktober-November lebih tinggi daripada periode lainnya.Pola diurnal petir di Sumatera Barat bertepatan dengan pola pergerakan awan dari lauatan ke daratan Sumatera, sebagaimana dilaporkan oleh penelitian sebelumnya. Petir dan hujan konvektif dalam dominan terjadi pada siang dan malam hari (16.00-20.00 WIB), khususnya di daratan. Hujan stratiform lebih sering terjadi pada sore hingga dini hari (16.00-04.00 WIB) di daratan dan 00.000-12.00 WIB di lautan.

Research paper thumbnail of A satellite study of the mid-latitude trough in electron density and VLF radio emission during the magnetic storm of 25 - 27 May 1967

J Atmos Sol Terr Phys, 1973

ABSTRACT

Research paper thumbnail of Modelling and analysis of substorm-related chorus events

The substorm-related chorus event is a recognised VLF signature of the substorm expansion phase. ... more The substorm-related chorus event is a recognised VLF signature of the substorm expansion phase. Computer simulations support the contention that these events are generated by cyclotron resonance between whistler mode waves and energetic electrons which drift into a ground station's field of view from an injection site near midnight.

Research paper thumbnail of Whistler-lightning correlations: tetrachoric index and similarity measures

Research paper thumbnail of Lightning here, whistlers there

Research paper thumbnail of Departures from sinusoidal variation in the occurrence of lightning in Equatorial Africa

Research paper thumbnail of Digital VLF Recording and Analysis System for SANAE--IV

Research paper thumbnail of Overview of VLF Radio Wave Activity at SANAE IV During 2002

Research paper thumbnail of Role of Anisotropy in the Simulation of Substorm Chorus Events

Research paper thumbnail of A Simple Model for Wave Growth Leading to Substorm Chorus Events

Research paper thumbnail of SANAE Observations of Substorm-Related Chorus Events

Research paper thumbnail of Seasonal and diurnal variations in lightning over Southern Africa and the effect of warm ocean currents

Research paper thumbnail of Whistler-lightning correlations: tetrachoric index and similarity measures

Research paper thumbnail of Sinusoidal Variation of Lightning Activity over Africa

Research paper thumbnail of Co-ordinated Observations of Sprites

Research paper thumbnail of The Conjugate Sprite Campaign---A potential north-south collaborative project for the International Heliophysical Year

Research paper thumbnail of The Conjugate Sprite Campaign: A Potential North-South Collaborative Project for the IHY

Red sprites are luminous phenomena which occur at high altitude above thunderstorms. It is though... more Red sprites are luminous phenomena which occur at high altitude above thunderstorms. It is thought that a beam of relativistic electrons may be generated during the formation of a red sprite and that this beam should travel along a magnetic field line to the conjugate hemisphere. A campaign was organised to detect evidence of this energetic electron beam. During the

Research paper thumbnail of Simulation of substorm chorus events

The Substorm Chorus Event (SCE) is a VLF radio phenomenon which may be observed after the onset o... more The Substorm Chorus Event (SCE) is a VLF radio phenomenon which may be observed after the onset of the substorm expansion phase. It consists of a band of VLF chorus emissions with rising upper and lower cutoff frequencies. These emissions arise from cyclotron resonance between whistler mode waves and energetic electrons which drift into a station's field of view from an injection site around midnight. Particle tracking simulations are used to understand the nature of these events. Specifically, consideration of changes in the degree of anisotropy of the particles within a station's field of view and the resulting implications for cyclotron resonance instability produce simulated events in good agreement with observations.

Research paper thumbnail of First observations of Trimpi Events at Durban ( L = 1.69) using an OMSKI Receiver

Journal of Geophysical Research, 1993

ABSTRACT

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