Variations in meteor heights at 22.7°S during solar cycle 23

• The relationship between meteor height at 23°S and solar flux has been discussed.
• Meteor peak height showed linear decrease of 30–38 m/year when MgII-F10.7 was used.
• The behavior of the meteor peak height was in phase with the solar flux.
• Meteor echoes are weaker and decay times are reduced during solar minimum years.
• Meteor height decrease is thought as being due to a drop in upper atmosphere density.

The meteor radar measurements obtained at Cachoeira Paulista (22.7°S), Brazil, have been used to study a possible relationship between meteor echo height variations and solar flux during solar cycle 23. A good concordance between the normalized values of the annual mean of the meteor peak heights and F10.7 solar radio flux and Mg_II solar indexes have been observed during declining phase of the solar cycle 23. After eliminating the solar activity influence, the annual mean of the meteor echo peak heights showed a linear decrease of 30 m/year when Mg_II solar index is used and 38 m/year when F10.7 solar radio flux is used. When the trend is eliminated the relationship between meteor peak heights and F10.7 solar flux indicate a trend of 672 m/100 sfu (sfu-solar flux unit). The meteor amplitude signals and the decay time drops after mid-2004, which may be attributed to the decreasing of the electron density in the meteor trails. The meteor echo peak height decrease has been interpreted as being caused by a reduction in air density in the upper atmosphere.