The first low radio frequency ( < 1.4 GHz ) detection of the outburst of the recurrent nova RS Ophiuchi is presented in this letter .
Radio emission was detected at 0.61 GHz on day 20 with a flux density of \sim 48 mJy and at 0.325 GHz on day 38 with a flux density of \sim 44 mJy .
This is in contrast with the 1985 outburst when it was not detected at 0.327 GHz even on day 66 .
The emission at low radio frequencies is clearly non-thermal and is well-explained by a synchrotron spectrum of index \alpha \sim - 0.8 ( S \propto \nu ^ { \alpha } ) suffering foreground absorption due to the pre-existing , ionized , warm , clumpy red giant wind .
The absence of low frequency radio emission in 1985 and the earlier turn-on of the radio flux in the current outburst are interpreted as being due to higher foreground absorption in 1985 compared to that in 2006 , suggesting that the overlying wind densities in 2006 are only \sim 30 \% of those in 1985 .