Bhowmik, K B

De, Barin Kumar

Rai, Pinaki

IACS Institutional Repository

,„j,an J. Phys. 75B (3), 255-257 (2001)U P  B— an intemational journalSudden rise in amplitude of 40 kHz radio signal in relation to solarradio fluxB a rin  K u m a r D e* , K  B B h o w m ik  an d  P in ak i Pal Department of Physics. Tripura University, Suryamaninagar-799 130, Tripura, India E-mail luphysic@dic vsnl net luAbstract The paper reports the experimental observations of isolated short period enhancements in amplitude of 40 kHz radio signal transmitted from Sanwa, Japan to KLolkata, India m relation to solar radio bursts having peak flux greater than 1000 m the unit of 10 * ’ Wm  ^ Hz ' The delay between commencements of signal amplitude and solar radio bursts lies between 3 and 12 minutes The signal Liilianccmcnt in dB exhibits linear increase with increase of solar radio flux up to 8000 flux unit The emission of hard X-rays associated with solar radii) hursts can cause extra ionization in the D-region of ionosphere As a result, conductivity parameter in wave guide mode theory is changed to allow better reflection This fact is the cause of enhancement of signal amplitudeKeywords Solar radio emission and X-rays, radio propagation, ionosphere.PA(;S INos. 94 20 Ee, 96 60.Tf1. In tro d u c tio nI he D -region o f  th e  io n o s p h e re , a t a lt i tu d e  b e tw e e n  6 0  an d  ^0 km, is m a in ly  fo rm e d  d u e  to  io n iz a tio n  o f  n itr ic  o x id e  (NO) b y  L y m a n -a  ra d ia tio n  a n d  fro m  io n iz a tio n  o f  m o le c u la r  oxygen (O 2) a n d  n i t ro g e n  (N 2 ) b y  X -ra y s  o f  w a v e le n g th  smellier than  10 A . It is w e ll  e s ta b lish e d  [1 ,2 ]  th a t La rad ia tions an d  s o la r  X - ra d ia t io n s  a re  c lo s e ly  c o rre la te d  w ith  solar m icrow ave  ra d ia tio n s . S o  it is e x p e c te d  th a t D -re g io n  ot the io n o sp h ere  w ill b e  a p p re c ia b ly  a f f e c te d  d u e  to  in c re a se  ol so la r  rad io  e m is s io n .2. O b se rv a tio n s  a n d  r e s u l t sIhc am plitude o f  4 0  k H z  ra d io  s ig n a l (C a ll s ig n  : J 0 2 A S /  JJF-2) tran sm itted  fro m  S a n w a , 3 6 °1 1 * N , 1 3 9 ‘^ 51’E ) h a s  ^een reco rded  in  a  d iu m a l b a s is  in  th e  D e p a r tm e n t o f  Physics, T rip u ra  U n iv e rs ity . T h e  re c e iv in g  sy s te m  c o n s is ts  j loop a n ten n a  fe e d in g  a  n u m b e r  o f  O P  A M P s  u se d  in  radio f re q u e n c y  m o d e . T h e  o u tp u t  o f  A C  a m p lif ie r  an d  ihe DC level a re  fu r th e r  a m p lif ie d  lo g a r itm ic a lly . T h e  D C  is u sed  a s  th e  s ig n a tu re  o f  a m p litu d e  o f  4 0  k H z  signal. T he o v e ra l l  g a in  o f  th e  a m p lif ie r  is 120 d B  w ith  a* ^ oncsponding Authorb an d  w id th  o f  2 0 0  H z. T h e  g re a t c irc le  d is ta n c e  b e tw een  A g a rta la  (2 3 °N , 9 r E )  a n d  S an w a  ( 3 6 ° i r N ,  1 3 9 ° 5 r E )  is 4 8 8 4  km .T h e  am p litu d e  o f  th e  re c o rd e d  s ig n a l is la rg e r  a t  n ig h t th a n  a t d ay . T h e  su n r ise  a n d  su n se t e f fe c ts  a re  a lso  c h a ra c te r is tic  fe a tu re s  o f  th e  s ig n al. T h e  s ig n a l a m p litu d e  e x h ib its  e n h a n c e m e n t d u rin g  X -ray  fla res . T y p ic a l zigzag v a ria tio n s  a re  a lso  o b se rv e d  d u e  to  m e te o r  sh o w ers . Q u asi-  p e r io d ic  v a ria tio n s  a re  o b se rv e d  d u rin g  n ig h ts  fo llo w e d  by  h ig h  g e o m a g n e tic  ac tiv ity .A p a rt fro m  a ll th e  o h a ra c te ris tic  v a r ia tio n s , it  is  n o te d  th a t th e  s ig n a l o c c a s io n a lly  e x h ib its  iso la te d  sh o rt p e r io d  su d d e n  en h a n c e m e n ts . Iso la te d  in  th e  se n se  th a t th e  s ig n a l lev e l is a lm o s t s tra ig h t lin e  w ith in  ± 2  h o u rs  o f  th e  e v e n t c o n s id e re d . T w o  s a m p le s  o f  e v e n ts  a rc  p ro d u c e d  in  F ig u re  1.D u rin g  th e  p e r io d  fro m  Ju ly  1993 to  Ju n e  1994 , w e h av e  re c o rd e d  57 su ch  e v e n ts  o u t o f  w h ic h  4 4  a rc  c o rre la te d  w ith  o u ts ta n d in g  o c c u rre n c e s  o f  so la r  ra d io  e m iss io n  o f  sh o rt d u ra tio n  an d  h a v in g  p e a k  f lu x  g re a te r  th an  1000  in th e  u n it© 2001 I ACS256 Barin Kumar De, K B Bhowmik and Pinaki Palo f  10^^^ W  m   ^ H z ' .  S o la r  rad io  b u rs ts  at v a rio u s fixed  fre q u e n c ie s  a re  re p o r te d  by  the w o rld w id e  n e tw o rk  o fv aria tio n  e x h ib its  a  sa tu ra tio n  p ro p e rty  a fte r  8 0 0 0  flux unii It is w o rth  m en tio n in g  th a t fo r  e v e n ts  re la te d  to  so la r bursts26252423222120(b ) 1 2 -1 0 -1 £  ■L ^  8 -Vb’§  6 -UJ1 20 30 40 ^  4 -OriMI' IN MINUTHSF ig u re  I. Record o f  cnhanccnicnl in 40 kHz signal in relation lo solar radio bursts Signal enhancem ent is in term s o f  induced voltage in dH above ] |.iV (a) C orresponding to solar burst on 05-10-1*^93 at 16—47 Hour, 1ST w ith peak flux ol 1900 unit. The 0-m m ule corresponds lo 16-50 Hour, I S r  and (b) C orresponding to solar burst on 05-01-1994 at 14-28 Hour, IS'l with peak flux o f  1200 unit The 0-m m utc corresponds lo 14-15 Hour, IS !o b se rv in g  s ta tio n s . T h e  o b se rv a tio n s  a re  ta k e n  from  S o la r G eo p h y sica l D ata  B ook , p u b lished  by  N O A A , U S D ep artm en t o f  C o m m erce .T h e re  is a d e la y  in th e  c o m m e n c e m e n t o f  su d d en  en h an cem en t o f  4 0  k H z  s ig n a l w ith  re sp e c t to  so la r  rad io  b u rs ts . T h e  d e lay  tim e ran g es  from  3 m in s to  12 m ins. T he d is tr ib u tio n  o f  d e la y  tim e  h as b een  sh o w n  in F ig u re  2. F o re9LUUu81000 10000S01.AR RADIO FLUXDELAY TIME (S)F ig u re  2. D istribution  o f  signal enhancem ent events in various ranges o f  delay tim e5 0 %  o f  th e  e v e n ts  d e lay  tim es are  b e tw een  3 m ins an d  6 m in s. T h e  m a rk e d  fea tu re  is th a t th e  d e lay  tim e  is at least 3 m ins.T h e  e n h a n c e m e n t ev en ts  re la te d  to  so la r bu rsts o f  d u ra tio n s sm a lle r  th an  5 m in s  a re  32  in n u m b er. In th is  c ase  s ignal e n h a n c e m e n t sh o w e d  a  sy s tem a tic  v a ria tio n  w ith  so la r  rad io  p e a k  flux . In  F ig u re  3 w e sh o w  th e  v a ria tio n  o f  s ignal e n h a n c e m e n t w ith  p e a k  flux  o f  a sso c ia te d  b u rs ts . T h eF ig u re  3. T he varia tion  o f  40  kH z signal am plitude cnhnnccmeni (in dB) w ith the varia tion  o f  solar radio flux in the 10 Wm * H/ ‘o f  d u ra tio n  g re a te r  th a n  5 m in s d id  n o t e x h ib it such  graphical re la tio n .3 . D isc u s s io nT h e  d o m in a n t p ro c e s s  o f  e le c tro n  p ro d u c tio n  in th e  quiescent D -re g io n  is th e  p h o to io n iz a tio n  o f  n itric  ox id e  by L,,- ra d ia tio n  [3]. A lth o u g h  th e  c o n tr ib u tio n  o f  th e  so lar X-ravb to  th e  fo rm a tio n  o f  D -re g io n  is sm a ll, it is estab lished  that so la r X -ray s  a t <  10 A are  c e r ta in ly  re sp o n s ib le  for extra­io n iza tio n  in th e  D -reg io n  [4 ,5 ]. T h e  e m iss io n  o f  hard X-rays a sso c ia te d  w ith  so la r  ra d io -b u rs t can  c a u se  extra-ionization in th e  D -reg io n  o f  io n o sp h e re  lo w e rin g  th e  no rm al reflection h e ig h t from  70  k m  to  6 0 -6 5  km . T h e re  a re  tw o  competing p ro c e sse s  ca u se d  b y  in c rea se  in e le c tro n  d en sity , -a  decrease in h e ig h t o f  th e  e a r th - io n o sp h e re  w a v e g u id e  (responsible ior su d d en  d e c re a se  in  s ig n a l a m p litu d e )  an d  an increase in the c o n d u c tiv ity  o f  th e  u p p e r  b o u n d a ry  o f  th e  w avegu ide  due to s teep e r e lec tro n  d en sity  g rad ien t w h ich  a llo w s b e t t e r  reflection[6]. W ith  re sp e c t to  w a v e le n g th  o f  p re se n t signal, the later is d o m in a n t an d  w e o b se rv e  e n h a n c e m e n t.W e h ilig h t th e  fa c t th a t e n h a n c e m e n t in  4 0  kH z signal a m p litu d e  is o n ly  a p p re c ia b ly  re la te d  w ith  so la r  radio  bursts o f  sm all d u ra tio n s , sm a lle r  th an  5 m in s. S o  it is concluded th a t a s so c ia tio n  o f  h a rd  X -ra y s  in c re a se s  w ith  impulsiveness o f  so la r  ra d io  b u rs ts .A c k n o w le d g in e i i tT h e  au th o rs  a re  th a n k fu l to  P ro f . A  K  S en  and  P ro f S  ^S a rk a r o f  C a lc u tta  U n iv e rs ity  fo r  th e ir  v a lu a b le  suggestions in th is w o rk .Sudden rise in amplitude of 40 kHz radio signal in relation to solar radio flux 257HcftrciicM |4] M Nicolet and Aikin J Geophys Res. 65 1469 (I960)[„ j A Fargusan. D G Morf.l and P M Harsen Radio Sc, 20 52* ,5, g D Dcspande and A P Milra ^ Aims Terr. Phys. 34 255(1985) (1572)ri 1 01 Pintado and S M Radicella J Atmos Terr Phys. 49 129 (1987) - ^ ^ ^^ arkar and 0  K l)e Ann Geophysicae 12 1119 |3] M Nicict Mem, Inst. MeteoroL Belg 19 83 (1987) (1994)

Sudden Rise in Amplitude of 40 kHz Radio Signal in Relation to Solar Radio Flux

http://arxiv.iacs.res.in:8080/jspui/bitstream/10821/6315/1/Sudden%20Rise%20In%20Amplitude%20of%2040%20Khz%20Radio%20Signal_Barin%20Kumar%20De.pdf

Sudden Rise in Amplitude of 40 kHz Radio Signal in Relation to Solar Radio Flux

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