Dis u bances o he wes e n Eu opean ionosphe e du ing he
o al sola eclipse o 11 Augus 1999 measu ed by a wide
ionosonde and ada ne wo k
T. Fa gesa, J.C. Jodogneb, R. Bam o dc, Y. Le Rouxd, F. Gau hie d, P.M. Vilae; ∗,
D. Al adill , J.G. Sole , G. Mi og
aCEA=LDG, BP 12, 91860 B uye es-le-Chˆa el, F ance
bGeophysics Di ision I.R.M. 3, A e Ci culai e, 1180 B ussels, Belgique
cRAL, Chil on, Didco Oxon, UK
dCNE=DMR=TSI, F ance Telecom, 2 A e P. Ma zin, 22301 Lannion Cedex, F ance
eCETP=CNRS, 4 A e Nep une, 94 107 S Mau -des-Foss6es Cedex, F ance
Obse a o i d’Eb e, 43520, Roque es, TARRAGONA, Spain
gEl ARENOSILLO Space Science Di ision, Mazagon-Mogue , 2110 HUELVA, Spain
Abs ac
The 11 Augus 1999 Sola eclipse o ali y pa h an ac oss wes e n Eu ope a nea -cons an la i udes o abou 49◦N. I
occu ed a mid- ime o a sequence o h ee days wi h s eady sola wind and quie magne osphe ic condi ions. I s esponse
was obse ed by a sco e o ionosphe ic acili ies, which will p o ide high- esolu ion p obing o he a ious dis u bances. Fi s
esul s allow us o compa e he ime =uc ua ions a a ious dis ances om o ali y on he eclipse and adjacen days, inside a
5◦Wes o 5◦Eas longi ude a ea. In his p elimina y wo k he oF1 and oF2 ime changes a e p esen ed in con ou maps
on a 50 km size g id. They show he expec ed longi ude ansi o eclipse pe u ba ion. We en u e b ie commen s on he
eclipse-own signa u es as sepa a e om he a ious wa e oscilla ions de ec ed p io o eclipse ime by 12.4 MHz pano amic
azimu h scans o he Losque ada nea Lannion (B i anny).
Keywo ds: Ionosphe ic dis u bances; Sola eclipse
1. In oduc ion
Sola eclipses a e s udied by ionosphe is s om he be-
ginning o he ionosphe e s udies (Ra cliAe, 1956). Thei
dis u bances p o ide a unique oppo uni y o unde s and he
ionosphe e o ma ion and dynamic p ocesses. The loss a e
o he F egion ha e been well analyzed by se e al au ho s
(Rishbe h, 1968). Since 1970, a new in e es has isen in so-
la eclipse s udies, abou he p opaga ion o a g a i y wa e
gene a ed by he a mosphe ic cooling in he Moon shadow
∗Co esponding au ho . Tel.: +33-1-45-11-4237.
E-mail add esses: [email p o ec ed] (T. Fa ges),
[email p o ec ed] (P.M. Vila).
(Chimonas and Hines, 1970). When a sola eclipse aAec s a
quie -pe iod ionosphe e, we ha e a chance o d awing c u-
cial es s abou he cha ac e is ic esponse o he ionosphe ic
plasmas o he se o pe u ba ions imposed by he s ong and
well-deGned occul a ion o he EUV and IR sola adia ion.
Howe e , ecu en ionosphe ic sola eclipse s udies ha e
b ough many inconclusi e esul s. No wo sola eclipses
p oduce he same plasma mo ion dis u bances because, he
luna cone a el geome y and i s angula eAec s on ou
magne ized plasmas a e diAe en each ime (in ac ou e-
sul s sugges a longi ude di e si y o he dis u bance be ween
i s p e-noon and pos -noon phases). The p esen e en ben-
eG ed om he dense Wes Eu opean ionosphe ic ne wo k,
and is a challenge o a mosphe e and ionosphe e models
Fig. 1. Map o he o al sola eclipse pa h a 200 km heigh on Augus 11, 1999, abo e Wes e n Eu ope. Loca ion o e ical incidence
ionosondes used in he pape is indica ed wi h ci cles.
e.g. TGCM (Ridley e al., 1984; Roble e al., 1986), CTIP
(MJ
ulle -Woda g e al., 1998)).
The imp o emen s in coope a ion and communica ion
among Eu opean obse e s g ea ly acili a ed he compila-
ion o da a. This allowed di ec compa ison o apid a i-
a ions in i ual heigh ionosphe ic p oGles and in he a i-
ous ue heigh - equency a ia ions. Fig. 1 is a gene al map
o he eclipsed ea h domain wi h he ame encompass-
ing ou p esen Wes Eu opean a ea o s udy, expanded in
Fig. 4. The magne ic ac i i y indices we e no ably weak on
he 10;11 and 12 Augus 1999 wi h Kp alues o 9;12+ and
15+, espec i ely. The sola =ux F10.7 was o 128. This
makes i easie o isualize he main p ocesses ha dis u bed
he plasma on he eclipse day.
We he e p esen a G s look assessmen o he simul a-
neous measu emen s om 12 e ical incidence (VI) iono-
sondes and some auxilia y ada s. This apid communica ion
pape deals he e o e wi h: a desc ip ion o he expe imen-
al de ice and a quali a i e desc ip ion o he mos salien
eclipse cha ac e is ics, as well as g a i y wa e and o he
oscilla ions obse ed du ing he eclipse and on Augus 12,
selec ed as con olled day in Sec ion 2; Some qua e -hou ly
2D maps o he oF1 and oF2 eclipse e olu ion o e he
geog aphic a ea: 5◦Wes o 5◦Eas by 35◦ o 55◦No h in
Sec ion 3; commen s on he a ious pe u ba ions isible on
he p esen aw da a, and on g a i y wa e ypology, com-
pa ing he analogy a ia ions in 2D- ime ac oss he Wes
Eu opean ne wo k in Sec ion 4.
2. Measu emen s in Wes e n Eu ope du ing he sola
eclipse
2.1. Expe imen al de ice
The obse a ion o his sola eclipse beneG ed om an ex-
cep ional expe imen al co e in Wes e n Eu ope. We p esen
in Table 1, he cha ac e is ics o he 12 ionosondes used,
wi h loca ion, ime esolu ion and maximum sola obscu a-
ion a 200 km heigh .
The HF sounding ne wo k o he Labo a oi e de De ec-
ion e de Geophysique consis s o a ansmi e loca ed
in F ancou ille (FRC) and o h ee ecei e s which ha e
been se in a adius o 60 km o FRC. The expe imen
is based on he p opaga ion o an HF wa e be ween a
ansmi e and a ecei e h ough he ionosphe e. This HF
wa e is e=ec ed when i s equency is equal o he plasma
equency along he p opaga ion pa h. Two sounding me h-
ods a e used in pa allel. The G s me hod is e ical inci-
dence ionog ams which gi es he elec on densi y p oGle
abo e FRC. The second me hod measu es phase shi s
due o ionosphe ic mo ions as g a i y wa es, o a elling
ionosphe ic dis u bances (TID). Phase shi s a e measu ed
by ada equency Dopple spec a, which de e mine he
e ical speed a he e=ec ion poin . I an i ine an pe u -
ba ion aAec s he h ee links successi ely, he ho izon al
componen o he pe u ba ion eloci y is de e mined by
iangula ion.
Table 1
Loca ion o he ionosondes used du ing he eclipse measu emen s wi h hei ime esolu ion and hei maximum sola obscu a ion a
200 km heigh
S a ion Longi ude La i ude Time esolu ion Maximum sola obscu a ion
(min) a 200 km heigh (%)
F ancou ille 1:7◦E48:4◦N 1 100.0
Lannion 3:45◦W48:7◦N 1 100.0
Hels on 5:3◦W50:1◦N 5 98.7
Dou bes 4:6◦E50:1◦N 10 96.2
Chil on 1:3◦W51:7◦N 4 92.3
Poi ie s 0:3◦E46:6◦N 15 92.1
Roma 12:5◦W41:9◦N 5 83.3
Cailhau 2:1◦E43:1◦N 0.5 81.2
Wa shaw 21◦W52
◦N 5 79.1
Julius uh 13:4◦E54:6◦N 10 75.9
Eb e 0:3◦E40:8◦N 5 71.6
El A enosillo 6:7◦W37:1◦N 15 55.7
Ionog am esul s a e p esen ed in his pape while he
Dopple da a will be ho oughly s udied in a u u e pape .
The Losque oblique baksca e ada sounded olumes
o he ionosphe e a g oup-pa h dis ances o 300–1200 km
om he ada , comple ing he VI ionosonde ne wo k.
2.2. Losque ada esul s
The Losque ada acili y, nea Lannion, has a ci cula
a ay o 120 an ennae scanned e e y 1.5 min. Du ing he
eclipse expe imen , he equency used was 12.4 MHz wi h
an ele a ion angle a ound 30◦. Any deple ion in he F laye
causes deepe pene a ion o he sounding wa e, hus longe
g oup pa h.
The oblique soundings p esen ed in Fig. 2 co espond o
F egion e=ec ing a eas om h ee azimu hs (each panel
showing wo azimu h plo s), espec i ely, loca ed a ound
he No he n I ish Sea (00–03◦), he Sou he n Sco land Eas
coas (24–27◦), Sou h-Eas o F ance (138–141◦, Hau e
P o ence) and No h-Wes o Spain (198–201◦). The ange
scale is gi en in e u n backsca e g oup pa h; hence he
a ge is loca ed a hal his ange.
Bo h no hwa d sequences show eclipse-cen e ed holes
o wid h apidly changing wi h azimu h, while he Sou h-
Eas wa d eco d clea ly e idences a pene a ion dis u bance
o opposi e symme y o ha o he no hwa d sigh ings. Fo
all azimu hs he u hes g oup pa h ime coincides exac ly
wi h he maximum obscu a ion ime in he a ge e=ec ion
a ea conce ned. The Sou h-Eas o Sou h-Wes -o ien ed se-
ies e eals wide and shallowe eclipse deple ions.
The eclipse hole is qui e clea in he No h wi h a
on al slope a 0920 UT, while a simila on o No h
No h-Eas s a s a 1010 UT. The hole is deepes in he
No h No h-Eas whe e he a ge is loca ed nea es o he
eclipse o ali y pa h.
P e-eclipse oscilla ions iewed in his h ee azimu hs
we e widely diAe en ; wi h a s ong (non-eclipse) wo hou
quasi-pe iod wa e in he No h, a ain o h ee wa es o
abou 50 min in No h No h-Eas , and wi h much weake
=uc ua ions owa d 140◦E. A ound 0830 UT on 201◦and
0900 UT on 24◦, a clea inc ease o g oup pa h indica es a
No h-Eas wa d mo ing deple ion.
2.3. Ionog am esul s
Fig. 3 shows wo se s o da a eco ded a F ancou ille
and Eb e on Augus 11 and 12, 1999. The F ancou ille
ionosonde was loca ed jus unde he o al sola eclipse pa h
in he ionosphe e be ween 130 and 250 km heigh on ac-
coun o he sola zeni hal angle (53◦a he maximum obscu-
a ion ime). The sola obscu a ion maximum o he Eb e
ionosonde was 71%.
F ancou ille esul s: Compa ing measu emen s eco ded
on Augus 11 and 12, bo h oF1 a ia ions a e iden ical ou -
side he eclipse ime in e al, ollowing a Chapman law;
inside his ime in e al, oF1 alues on Augus 11 a e
lowe han on Augus 12. The maximum pho ochemical oF1
eclipse all o 37% is eached a 1023 UT when he Sun is
o ally eclipsed.
In he F1 laye , he s a o he eco e y phase (when oF1
begins again o inc ease) is synch onous wi h he end o he
o al sola eclipse (1023 UT). Howe e , he s a o he F2
laye eco e y phase is 20 min a e he local maximum oc-
cul a ion (99%). This obse a ion ag ees well wi h p e ious
esul s (Cohen (1984): 20–50 min; Salah e al. (1986): 20
–30 min; Walke e al. (1991): 20–40 min; Kolokolo e al.
(1993): 30–45 min; A aimo ich e al. (1998): 10 min).
Eb e esul s: The maximum oF1 dec ease is eached
nea ly a he maximum obscu a ion ime wi h 24%. The 19%
all in oF2 alues lags by abou 15 min behind he maxi-
mum obscu a ion ime.
Fo he wo s a ions, as also o he o he s a ions no
shown he e, he oF2 d op du ing he sola eclipse is weak.
Fig. 2. Re u n g oup pa h e sus UT om Losque Island (Lannion) in ou diAe en azimu hs: 0–3◦, op panel; 24–27◦, second panel;
138–141◦, hi d panel and 198–201◦, bo om panel.
3. oF1 and oF2 con ou maps
Mo gan e al. (1978) p esen ed a s udy wi h Gne space
and ime esolu ion showing he e olu ion o TID. In his
pape , we do no use he echniques de eloped by Mo gan
e al. Fo hese p elimina y esul s, we p esen he la ge
ime (pe iod o abou 2 h) and space (abou 1000 km) scale
pe u ba ions in he wes e n Eu opean ionosphe e du ing he
11 Augus 1999 sola eclipse wi h he help o in e pola ed
e ical ionosonde c i ical equency maps.
Wi h ou ionosondes dis ibu ed on he same magne ic
me idian, Naga a e al. (1955) had d awn a 2D map o a sola
eclipse pe u ba ion a midday in he E egion whe e he
x-axis was ime and y-axis he dis ance be ween ionosondes
along he me idian.
Ha ing da a om 12 Eu opean ionosondes, we build in-
s an aneous maps in 2D ex ensions o he nea -cons an
heigh s o hMF1 (abou 190 km (Fa ges, 2000)) and hMF2.
T acing o iso- equency con ou s is done using a 2D in e -
pola ion me hod (Akima, 1978).
Fig. 3. oF1 and oF2 changes abo e F ancou ille and Eb e du ing he sola eclipse and ollowing hou s, he Augus 11, 1999 and du ing
he same in e al o ime on Augus 12, 1999. The s a and end imes o he sola eclipse a e shown wi h dashed e ical lines; he maximum
obscu a ion ime is indica ed wi h a do ed e ical line.
The indi idual oF1 eclipse ime plo s a e qui e accu-
a e ( o be e han 0.1 MHz excep o b ie in e als o
spo adic E occul a ion) and clea ly minimize a maximum
obscu a ion ime. Thus we can use he oF1 pa ame e
space =uc ua ions as indica o s o he eclipse dis o ions.
Fig. 4 p esen s en such qua e -hou ly maps be ween
0830 and 1045 UT and wo mo e a 1200 and 1300 UT.
The h ee si es loca ed u he Eas : Julius uh, Wa shaw and
Roma p o ided da a o he acing as bounda y alues. A
G s poin dese ing no ice is he wide la i ude ex en o he
eclipse plasma densi y deple ion, which exceeded 1300 km
adius a El A enosillo (sou he n Spain).
The eclipse deple ion should appea la e han 0900 UT
om he wes e n longi udes. F om 0830 o 0900 UT, he
hole obse ed Wes o he 0◦longi ude is p obably he
las eAec o he A lan ic la ge-scale g a i y-wa e appa en
on he Losque scans. The eclipse deple ion is maximum
a 1015 UT. I ecedes om 10:45 UT as expec ed by he

eas wa d Moon shadow mo ion. A 1200 UT, he sola
eclipse eAec s disappea comple ely. This pe u ba ion is oo
wide (a quasi-ci cle o diame e much la ge han 1000 km)
and oo as (a ound 790 m=s, ha is Moon shadow eloc-
i y) o be impu ed o any hing else han he sola eclipse. Fo
ins ance, he sou he nmos s a ion El A enosillo, abou
Fig. 4. Con ou maps o oF1 qua e -hou ly alues be ween 0830 and 1045 UT and be ween 1200 and 1300 UT d awn on a 50 ×50km
g id. An open ci cle is d awn on he eclipse pa h when he Moon shadow is p ojec ed on he ionosphe e (a 1015 and 1030 UT) a 200 km
heigh abo e Wes e n Eu ope.
1300 km om o ali y, measu ed deple ions o −20% on
oF1, −17% on oF2.
The peak a ound Cailhau a 1200 UT is possibly he G s
sign o an eme gen bow wa e. A 1300 UT abo e Eb e,
5.75 MHz con ou e eals a on al peak in F1 laye elec on
densi y, ha was obse ed on he indi idual Eb e plo in
Fig. 4. (Con inued).
Fig. 3. This wa e p opaga es sou hwa d a a ound 80 m=s.
I s p ope ies a e discussed in a companion pape (Al adill
e al., his issue).
Fig. 5 p esen s 12 qua e -hou ly oF2 maps be ween 0845
and 1130 UT. The Moon’s shadow a 300 km is plo ed on
he map. The eclipse dis u bance is delayed by abou 30 min
on he maximum obscu a ion ime, as isible in Fig. 3. The
1030 UT map shows a minimum oF2 a ea cen e ed on 4◦W
when he Moon’s shadow has al eady eached 7◦E.
Two episodes o oF2 deple ion occu , espec i ely, a
0945 and 1100 UT nea he 0◦longi ude and be ween 45
and 55◦la i ude.
4. Discussion
The main pu pose o ou discussion is o ela e he
wo 2D c i ical equency maps o he Losque ada scans.
Consis ency be ween he wo se s o measu emen s would
conG m he a ia ions and allow a Gne esolu ion mapping
o dis ances un il 1200 km om he Losque ada .
On Losque scans, he majo phenomenon is obse ed
be ween 0930 and 1130 UT as a la ge inc ease o g oup pa h
o 300 km. This deple ion is ob iously due o he eclipse
elec on densi y loss.
Fig. 5. Con ou maps o oF2 qua e -hou ly alues be ween 0845 and 1130 UT d awn on a 50 ×50 km g id. An open ci cle is d awn on
he eclipse pa h when he Moon shadow is p ojec ed on he ionosphe e (a 1015 and 1030 UT) a 300 km heigh abo e Wes e n Eu ope.
We will e e o wo ea u es mos no iceable on he
qua e -hou ly maps (0845 UT on oF1 and 1100 UT on
oF2), and o ano he eAec mo e appa en on he Losque
scans be ween 0930 and 1000 UT on he no he n azimu hs.
(1) We no iced in Sec ion 3 (Fig. 4) he impo an oF1
hole s a ing a 0845 in No h-Wes Spain which seems o
mo e o No h-Eas ac oss B i any owa d cen al England.
Fig. 5. (Con inued).
A esidual o he oF1 densi y hole obse ed on he wes a ea
om 0830 o 0930 UT is measu ed a FRC. The Dopple
measu emen s conG m he No h-Eas wa d displacemen .
The Losque scans on 198–201◦(0830 UT) and on 24–27◦
(0900 UT) conG m his deple ion and i s mo ion. We canno
p esen ly ela e his singula i y o any di ec eclipse eAec .
The non- i ial cha ac e o his hole and o i s displacemen
is p esen ly diNcul o in e p e .
(2) The oF2 deple ion a ound Poi ie s a 1100 UT (Fig.
5) can be compa ed wi h he 138–141◦scans om Losque
(Fig. 2). Fo his a ea and ime, he oF1 a ia ions a e
uni o m; he abno mal e=ec ion is he e o e aking place a
F2 laye le els be ween 650 and 900 km g oup pa h dis ance
om Losque . Looking back om Fig. 5 a 1100 UT, we
no ice a s eep densi y g adien in his di ec ion a ound he
700 km dis ance (sligh ly No h o Cailhau). P opaga ion