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Radio signals from India’s Mars Orbiter Mission (MOM) have been used to study turbulence in solar plasma during the post-maxima phase of the solar cycle 24. S-band (2.29 GHz) radio carrier downlink signals from MOM were received at Indian Deep Space Network (IDSN), Bangalore, and frequency residuals were spectrally analyzed to obtain coronal turbulence spectrum at heliocentric distances ranging between 4 and 20 R⊙ corresponding to coronal regions where solar wind primarily get accelerated. The frequency fluctuation spectrum relates to the turbulence regime in the near-Sun region. Turbulence power spectrum (temporal spectrum of frequency fluctuations) at a lower heliocentric distance (<10 R⊙), reveals flattening at lower frequencies regions, with spectral index αf ∼ 0.3 − 0.5 which correspond to solar wind acceleration region. For larger heliocentric distances (>10R⊙), the curve steepens with spectral index αf ∼ 0.7 − 0.8, a value close to 2/3, indicative of developed Kolmogorov-type turbulence spectrum. The findings are consistent with earlier results. Plausible explanations to support the theory of coronal heating by MHD waves and the acceleration of solar wind are presented. An insight into the feeble maxima of solar cycle 24 is discussed.

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